Big Ideas Math Algebra 1, 2015
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Big Ideas Math Algebra 1, 2015 View details
7. Graphing Absolute Value Functions
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Exercise 31 Page 160

Create two tables of values and then plot the graphs on the same coordinate plane.

Graph:

Comparison: See solution.

Practice makes perfect

To graph the functions without going through the entire process of transforming the parent function, we can make two tables of values. Then we only need to plot and connect the ordered pairs we find.

Graph

Let's begin with creating a table of values for a.

x |x+2|+3 a(x)
-3 | -3+2|+3 4
-1 | -1+2|+3 4
1 | 1+2|+3 6
3 | 3+2|+3 8
Now we do the same with function b.

x |-4x+2|+3 b(x)
-3 |-4( -3)+2|+3 17
-1 |-4( -1)+2|+3 9
1 |-4( 1)+2|+3 5
3 |-4( 3)+2|+3 13

Finally, we will plot and connect these ordered pairs. Keep in mind that the graph of an absolute value function has a V-shape!

Comparison

Note that we can rewrite b in terms of a. la(x)=|x+2|+3 b(x)=|- 4x+2|+3 ⇒ b(x)=a(- 4x) The graph of b is a horizontal shrink of the graph of a by a factor of 14, followed by a reflection in the y-axis. Note that the y-intercept is the same for both graphs.