Radical Functions & Graphing
Graph π¦ = βπ₯ using a table of values and state the domain and range.
Domain: Range:
Notice the domain is restricted. Why? What is an easy way to obtain the domain?
Radical functions can be graphed using transformations β just like quadratic functions! For example, π¦ = πβπ₯ β β + π. The vertex is (β, π), and the vertical expansion/compress is π. When graphing parabolas, what happened to π¦ = π₯2 when it became π¦ = βπ₯2 (ie. When the π value was -1)?
This is called a vertical reflection (a reflection through the _________________________). Therefore, graph π¦ = ββπ₯ without a table of values on the grid above, and then state the domain and range below:
What is the βbasic countβ for a radical graph? Right ____ Up _____ Remember, the π value alters the up/down count.
Graph π¦ = 3βπ₯ and π¦ = β12βπ₯ on the graph below & state the domain, range, x-int, y-int x y
To find the x-intercept, set y = 0.
To find the y-intercept, set x = 0.
Graph π¦ = βπ₯ + 3 + 2 and π¦ = β2βπ₯ β 1 β 4. Give D, R, x-int, y-int for each.
So, using transformation theory that was learned for quadratics, we can graph other types of functions with the same principles.
The graph π¦ = ββπ₯ is a reflection through the horizontal line through the vertex of the π¦ = βπ₯ graph. Using a table of values, graph π¦ = ββπ₯ below, and state the domain and range.
D: R:
On the grid above, graph π¦ = βββπ₯ without a table of values, and state the domain and range.
For the following radical functions, state the domain, range, x-int, and y-int. a) π¦ = β4βπ₯ β 3 + 8 b) π¦ =12βπ₯ + 5 β 1
Graph the following functions. A good way to do this is to locate the vertex first, and then establish the βcountβ from the vertex by altering the βbasic countβ accordingly.
a) π¦ = β4βπ₯ β 3 + 8 b) π¦ =12β4 β π₯ β 1
Here is a summary of transformations for radical graphs:
Graph the following and state the domain, range, x-intercept, and y-intercept π¦ β 6 = β2β3 β π₯
π = Β±πβΒ±(π β π) + π Steps for graphing:
1) If x is negative, factor it out. 2) Locate the vertex (h, k)
3) From the vertex, build the count:
If no negative in front in radical, go right. If negative in front in radical, go left.
If a is positive, count up. If a is negative, count down. Multiply up/down count by a value. Basic Count: right 1, up 1
right 4, up 2 right 9, up 3
Graphing π = π(π) πππ π = βπ(π)
The graphs of π¦ = π(π₯) and π¦ = βπ(π₯) could have different domains & ranges because of the restriction on an even root function.
Graph π¦ = π₯2 and π¦ = βπ₯2 and state the domain and range.
Graph π¦ =1
2(π₯ + 2)
2β 8 and π¦ = β1
2(π₯ + 2)
2β 8 and state the domain and range.
Absolute Value Equations What is the absolute value of a number?
Example 1 β Simplify a) |6| b) |β4| c) |β73
|
Example 2 β Solve |π₯| = 2
Steps for solving an absolute value equation:
1) Get the absolute value by itself on one side (everything not in the absolute value should be on the other side).
2) Set up two cases: the positive case and the negative case. Solve for each case. 3) Check each solution to see if it is an actual or extraneous solution.
Example 3 β Solve |π₯ + 7| = 10 First, by inspection:
Example 4 β Solve |π₯ β 2| + 3 = 9
Positive Case: Negative Case: Check:
Example 5 β Solve |3π₯ β 2| = 1 β π₯ algebraically
Example 6 β Solve |π₯ β 3| + 7 = 4
Example 7 β Solve |4π₯ β 5| + 2 = 2
Check:
Check:
An Absolute Value Equation with No Solution:
no solutions
Example 8 β Solve |π₯ + 5| = 4π₯ β 1 algebraicially Example 9 β Solve |π₯2β 7π₯ + 2| = 10 Example 10 β Solve |π₯ β 2| = π₯ β 2 Check: Check: quadratic absolute value equations
Absolute Value Functions & Graphing Example 1 β Graph π¦ = |π₯|
At times, absolute value functions are set up analogous to quadratic functions in standard form, using h, k, and a values to graph the function.
What is the basic count?
Summarize how each component of the function affects the graph:
π¦ = Β±π|π₯ β β| + π & π¦ = Β±π|β(π₯ β β)| + π
Example 1 β Graph each function and state the D, R, x-int, y-int:
a) π¦ = |π₯| β 3 b) π¦ = |π₯ + 4| x y -3 -2 -1 0 1 2 3 The graph π¦ = |π₯| consists of two graphs:
This is why an absolute value graph is called a piecewise function.
c) π¦ = β2|π₯| d) π¦ = β1
2|1 β π₯| + 2
e) π¦ + 7 = 3|2 β π₯| f) π¦ = 3 β14|π₯ β 2|
Look at (a) above. The right branch only would have the equation _______________ and the left branch only would have the equation _____________. Thus we can write
π¦ = |π₯| β 3 as a piecewise function:
If a graph is constructed for any function π(π₯), what will the graph for |π(π₯)| look like? Example 3 β Graph π¦ = π₯2β 4 using a table of values. Then graph π¦ = |π₯2β 4|
π₯ π(π₯) π₯ |π(π₯)|
4.5A β Rational Functions Part 1
A function π is a rational function if π(π₯) =π(π₯)
β(π₯), where π(π₯) and β(π₯) are polynomials.
The domain of π consists of all real numbers except π₯ values that make the denominator equal to zero (undefined values).
Example 1 β What are the undefined values for each rational function?
a)
π₯+52b)
π₯2π₯β4c)
π₯2β2π₯β15π₯+4d)
π₯π₯β72+16Graphing Rational Functions Example 2 β Graph π¦ = 1
π₯
D: R:
An asymptote is not part of the graph. A vertical asymptote is a line the graph
approaches as the denominator approaches zero. A horizontal asymptote Is a line the graph approaches as |π₯| gets larger. Not every rational function has both a horizontal AND vertical asymptote.
Vertical Asymptotes are found when the denominator equals zero. Sometimes the denominator must be factored to find the vertical asymptotes (see Example 1 above).
π₯ π¦ 1 2 3 10 100 1000 0 0.5 0.2 0.1 0.01 0.001 -1 -2 -10 -100 -0.5 -0.1 -0.01 -0.001
The function is not defined for π₯ = 0, so this is a vertical asymptote of the function, and is drawn as a dashed line. The pattern in the table can be written as:
as π₯ β 0+ , π(π₯) β +β as π₯ β 0β , π(π₯) β ββ as π₯ β +β , π(π₯) β 0+ as π₯ β ββ , π(π₯) β 0β
The line defined by π¦ = 0 is said to be a horizontal asymptote of the function, and is drawn as a dashed line.
Example 3 β Graph π¦ = 1
π₯β1
β 1
What is the vertical asymptote? Plot it. Now, complete the table of values below:
D: R: x-int: y-int:
Another way to think about the function above is using π¦ =π₯ββ1 + π, where the
intersection of the two asymptotes is (β, π). So, π¦ =π₯β11 β 1 is just like =π₯1 , but shifted one unit right and one unit down.
Before we graphed π¦ = 1
π₯β1β 1 above, we knew the vertical asymptote, but the
horizontal asymptote wasnβt apparent until after. How can we find the horizontal asymptote before?
The horizontal asymptote is the value that π¦ approaches as π₯ approaches Β±β. Consider the function (π₯) =π(π₯)β(π₯) :
1) If β(π₯) is a higher power than π(π₯), the horizontal asymptote is π¦ = π. 2) If π(π₯) and β(π₯) have the same power, the horizontal asymptote is
π¦ = πππππππ πππππππππππ‘ ππ ππ’πππππ‘ππ
πππππππ πππππππππππ‘ ππ πππππππππ‘ππ
3) If π(π₯) is a higher power than β(π₯), there is no horizontal asymptote. Letβs investigate all three cases:
a) π(π₯) = 1 π₯β2 b) π(π₯) = 1 π₯β2+ 3 c) π(π₯) = 2π₯ π₯2β4 d) 3π₯+1 π₯β2 e) π¦ = 3π₯(2π₯β1) 4π₯2β1 f) π¦ = π₯2 π₯ π₯ π¦ 2 0 1 -1+ -1000 1000
4.5B β Rational Functions Part 2 Example 1 β Graph π(π₯) = 1
π₯+3
D: R: x-int: y-int:
*To find the shape of the graph, itβs helpful to choose π values one less and one greater than vertical asymptote(s), and also π values approaching both horizontal and vertical asymptotes.
How would the graph be different if the function was π(π₯)
= β
π₯+31β 4 ?
Example 2 β Graph π¦ = 2π₯ π₯β1
D: R:
x-int: y-int:
π₯ π¦ π₯ π¦Example 3 β Graph β(π₯) =
2π₯2 π₯2+1 D: R: x-int: y-int: Example 4 β Graph π(π₯) = 2 π₯2βπ₯β2 D: R: x-int: y-int: Example 5 β Graph π¦ =π₯2β3π₯β4 π₯2+2π₯ D: R: x-int: y-int:*A note about horizontal asymptotes:
π₯ π¦
π₯ π¦
Rational Functions & Graphing Part 3 β βHolesβ
Sometimes, due to factoring and cancellation, a rational function simplifies, which can cause cancellation of parts of the denominator, resulting in the elimination of a vertical asymptote. This will create a βholeβ in the graph of the function.
Graph π = π+π
ππ+πβπ
D: Hole Coordinates: R:
Where there would have been a vertical asymptote, there is now just a βholeβ in the graph. For each of the following functions, determine any vertical asymptotes and the
coordinates of any holes a) π = π+π ππ+ππβπ
b) π = ππ+ππβπ πβπ
c) π(π) = π ππβππ π₯ π¦
Graph the function & state any asymptotes, hole coordinates, domain, range, x-int, y-int π(π) = β πβπ
ππβπβππ