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(1)

Higher Order Derivatives

Implicit Differentiation

Mathematics 53

Institute of Mathematics (UP Diliman)

(2)

For today

1

Higher Order Derivatives

2

Implicit Differentiation

(3)

For today

1

Higher Order Derivatives

2

Implicit Differentiation

(4)

Higher Order Derivatives

If

f

0

is differentiable, then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

, the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

, that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(5)

Higher Order Derivatives

If

f

0

is differentiable,

then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

, the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

, that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(6)

Higher Order Derivatives

If

f

0

is differentiable, then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

, the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

, that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(7)

Higher Order Derivatives

If

f

0

is differentiable, then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

,

the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

, that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(8)

Higher Order Derivatives

If

f

0

is differentiable, then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

, the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

, that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(9)

Higher Order Derivatives

If

f

0

is differentiable, then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

, the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

, that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(10)

Higher Order Derivatives

If

f

0

is differentiable, then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

, the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

,

that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(11)

Higher Order Derivatives

If

f

0

is differentiable, then the derivative of

f

0

is called the

second derivative

of

f

and is denoted

f

00

.

We can continue to obtain the

third derivative

,

f

000

, the

fourth derivative

,

f

(4)

,

and other

higher derivatives

.

Definition

The

n-th derivative of the function

f

, denoted

f

(

n

)

, is the derivative of the

(

n

1

)-th derivative of

f

, that is,

f

(

n

)

(

x

) =

lim

∆x

0

f

(

n

1)

(

x

+

x

)

f

(

n

1)

(

x

)

x

(12)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(13)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(14)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(15)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(16)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(17)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(18)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(19)

Higher Order Derivatives

Remarks

1

The

n

in

f

(

n

)

is called the order of the derivative.

2

The derivative of a function

f

is also called the first derivative of

f

.

3

The function

f

is sometimes written as

f

(0)

(

x

).

4

Other notations:

D

x

n

[

f

(

x

)]

,

d

n

y

dx

n

,

d

n

dx

n

[

f

(

x

)]

,

y

(

n

)

(20)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(21)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(22)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(23)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(24)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(25)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(26)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(27)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(28)

Higher Order Derivatives

Example

Find

f

(

n

)

(

x

)

for all

n

N

where

f

(

x

) =

x

6

x

4

3

x

3

+

2

x

2

4

.

Solution.

We differentiate repeatedly and obtain

f

0

(

x

)

=

6

x

5

4

x

3

9

x

2

+

4

x

,

f

00

(

x

)

=

30

x

4

12

x

2

18

x

+

4,

f

000

(

x

)

=

120

x

3

24

x

18,

f

(4)

(

x

)

=

360

x

2

24,

f

(5)

(

x

)

=

720

x

,

f

(6)

(

x

)

=

720,

f

(

n

)

(

x

)

=

0

for all

n

7.

(29)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(30)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(31)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1 2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(32)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(33)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(34)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3 2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(35)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(36)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(37)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5 2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(38)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(39)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(40)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7 2

·

(

2

)

=

15

(

2

x

3

)

72
(41)

Higher Order Derivatives

Example

Find

f

(4)

(

x

)

if

f

(

x

) =

2

x

3

.

Solution.

f

0

(

x

)

=

1

2

(

2

x

3

)

1

2

·

(

2

)

=

(

2

x

3

)

12

f

00

(

x

)

=

1

2

(

2

x

3

)

3

2

·

(

2

)

=

(

2

x

3

)

32

f

000

(

x

)

=

3

2

(

2

x

3

)

5

2

·

(

2

)

=

3

(

2

x

3

)

52

f

(4)

(

x

)

=

15

2

(

2

x

3

)

7

2

·

(

2

)

=

15

(

2

x

3

)

72
(42)

For today

1

Higher Order Derivatives

2

Implicit Differentiation

(43)

Equations in two variables are used to define a function explicitly or implicitly.

y

=

x

2

1

defines

f

(

x

) =

x

2

1

(explicitly).

y

2

=

x

+

1

defines two functions of

x

: (implicitly)

f

1

(

x

) =

x

+

1

f

2

(

x

) =

x

+

1

.

(44)

Equations in two variables are used to define a function explicitly or implicitly.

y

=

x

2

1

defines

f

(

x

) =

x

2

1

(explicitly).

y

2

=

x

+

1

defines two functions of

x

: (implicitly)

f

1

(

x

) =

x

+

1

f

2

(

x

) =

x

+

1

.

(45)

Equations in two variables are used to define a function explicitly or implicitly.

y

=

x

2

1

defines

f

(

x

) =

x

2

1

(explicitly).

y

2

=

x

+

1

defines two functions of

x

: (implicitly)

f

1

(

x

) =

x

+

1

f

2

(

x

) =

x

+

1

.

(46)

Equations in two variables are used to define a function explicitly or implicitly.

y

=

x

2

1

defines

f

(

x

) =

x

2

1

(explicitly).

y

2

=

x

+

1

defines two functions of

x

: (implicitly)

f

1

(

x

) =

x

+

1

f

2

(

x

) =

x

+

1

.

(47)

Equations in two variables are used to define a function explicitly or implicitly.

y

=

x

2

1

defines

f

(

x

) =

x

2

1

(explicitly).

y

2

=

x

+

1

defines two functions of

x

: (implicitly)

f

1

(

x

) =

x

+

1

f

2

(

x

) =

x

+

1

.

(48)

Equations in two variables are used to define a function explicitly or implicitly.

y

=

x

2

1

defines

f

(

x

) =

x

2

1

(explicitly).

y

2

=

x

+

1

defines two functions of

x

: (implicitly)

f

1

(

x

) =

x

+

1

f

2

(

x

) =

x

+

1

.

(49)

Equations in two variables are used to define a function explicitly or implicitly.

y

=

x

2

1

defines

f

(

x

) =

x

2

1

(explicitly).

y

2

=

x

+

1

defines two functions of

x

: (implicitly)

f

1

(

x

) =

x

+

1

f

2

(

x

) =

x

+

1

.

(50)

Consider: If

x

3

2

xy

3

y

6

=

0,

how do we find

dy

dx

?

Solution

From

x

3

2

xy

3

y

6

=

0

, we can define

y

explicitly in terms of

x

as

y

=

x

3

6

2

x

+

3

.

Thus,

dy

dx

=

(

2

x

+

3

)(

3

x

2

)

(

x

3

6

)(

2

)

(

2

x

+

3

)

2

=

4

x

3

+

9

x

2

+

12

(

2

x

+

3

)

2

.

(51)

Consider: If

x

3

2

xy

3

y

6

=

0,

how do we find

dy

dx

?

Solution

From

x

3

2

xy

3

y

6

=

0

, we can define

y

explicitly in terms of

x

as

y

=

x

3

6

2

x

+

3

.

Thus,

dy

dx

=

(

2

x

+

3

)(

3

x

2

)

(

x

3

6

)(

2

)

(

2

x

+

3

)

2

=

4

x

3

+

9

x

2

+

12

(

2

x

+

3

)

2

.

(52)

Consider: If

x

3

2

xy

3

y

6

=

0,

how do we find

dy

dx

?

Solution

From

x

3

2

xy

3

y

6

=

0

, we can define

y

explicitly in terms of

x

as

y

=

x

3

6

2

x

+

3

.

Thus,

dy

dx

=

(

2

x

+

3

)(

3

x

2

)

(

x

3

6

)(

2

)

(

2

x

+

3

)

2

=

4

x

3

+

9

x

2

+

12

(

2

x

+

3

)

2

.

(53)

Consider: If

x

3

2

xy

3

y

6

=

0,

how do we find

dy

dx

?

Solution

From

x

3

2

xy

3

y

6

=

0

, we can define

y

explicitly in terms of

x

as

y

=

x

3

6

2

x

+

3

.

Thus,

dy

dx

=

(

2

x

+

3

)(

3

x

2

)

(

x

3

6

)(

2

)

(

2

x

+

3

)

2

=

4

x

3

+

9

x

2

+

12

(

2

x

+

3

)

2

.

(54)

Consider: If

x

3

2

xy

3

y

6

=

0,

how do we find

dy

dx

?

Solution

From

x

3

2

xy

3

y

6

=

0

, we can define

y

explicitly in terms of

x

as

y

=

x

3

6

2

x

+

3

.

Thus,

dy

dx

=

(

2

x

+

3

)(

3

x

2

)

(

x

3

6

)(

2

)

(

2

x

+

3

)

2

=

4

x

3

+

9

x

2

+

12

(

2

x

+

3

)

2

.

(55)

Consider: If

x

3

2

xy

3

y

6

=

0,

how do we find

dy

dx

?

Solution

From

x

3

2

xy

3

y

6

=

0

, we can define

y

explicitly in terms of

x

as

y

=

x

3

6

2

x

+

3

.

Thus,

dy

dx

=

(

2

x

+

3

)(

3

x

2

)

(

x

3

6

)(

2

)

(

2

x

+

3

)

2

=

4

x

3

+

9

x

2

+

12

(

2

x

+

3

)

2

.

(56)

Implicit Differentiation

Question:

Suppose we have

x

4

y

3

7

xy

=

7

or

tan

(

x

2

2

xy

) =

y

.

How do we find

dy

dx

?

(57)

Implicit Differentiation

Question:

Suppose we have

x

4

y

3

7

xy

=

7

or

tan

(

x

2

2

xy

) =

y

.

How do we find

dy

dx

?

(58)

Implicit Differentiation

To find

dy

dx

using implicit differentiation, we

1

think of the variable

y

as a differentiable function of the variable

x

,

2

differentiate both sides of the equation, using the chain rule where necessary,

and

3

solve for

dy

dx

.

(59)

Implicit Differentiation

To find

dy

dx

using implicit differentiation, we

1

think of the variable

y

as a differentiable function of the variable

x

,

2

differentiate both sides of the equation, using the chain rule where necessary,

and

3

solve for

dy

dx

.

(60)

Implicit Differentiation

To find

dy

dx

using implicit differentiation, we

1

think of the variable

y

as a differentiable function of the variable

x

,

2

differentiate both sides of the equation, using the chain rule where necessary,

and

3

solve for

dy

dx

.

(61)

Implicit Differentiation

To find

dy

dx

using implicit differentiation, we

1

think of the variable

y

as a differentiable function of the variable

x

,

2

differentiate both sides of the equation, using the chain rule where necessary,

and

3

solve for

dy

dx

.

(62)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(63)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(64)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(65)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(66)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(67)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(68)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(69)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(70)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(71)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

3

·

dy

dx

0

=

0

3

x

2

2

y

2

x

·

dy

dx

3

·

dy

dx

=

0

2

x

·

dy

dx

+

3

·

dy

dx

=

3

x

2

2

y

dy

dx

(

2

x

+

3

)

=

3

x

2

2

y

(72)

Implicit Differentiation

Example

Find

dy

dx

if

x

3

2

xy

3

y

6

=

0

.

Solution.

D

x

[

x

3

2

xy

3

y

6

]

=

D

x

[

0

]

D

x

[

x

3

]

D

x

[

2

xy

]

D

x

[

3

y

]

D

x

[

6

]

=

D

x

[

0

]

3

x

2

2

1

·

y

+

x

·

dy

dx

References

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