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 29 Page 160

Create two tables of values and 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 obtained points and compare the graphs.

Graph

Let's begin with creating a table of values of function p.

x |x+1|-2 Simplify p(x)
-5 | -5+1|-2 |-4|-2 2
-3 | -3+1|-2 |-2|-2 0
-1 | -1+1|-2 |0|-2 -2
1 | 1+1|-2 |2|-2 0
3 | 3+1|-2 |4|-2 2
Now let's do the same with function q.

x |1/4x+1|-2 Simplify q(x)
-5 |1/4( -5)+1|-2 |-1/4|-2 -1 34
-3 |1/4( -3)+1|-2 |1/4|-2 -1 34
-1 |1/4( -1)+1|-2 |3/4|-2 -1 14
1 |1/4( 1)+1|-2 |1 14|-2 -3/4
3 |1/4( 3)+1|-2 |1 34|-2 -1/4

Finally we can plot these ordered pairs on one coordinate plane.

Comparison

We can rewrite q(x) as p( 14x), which is a horizontal stretch of p(x) by a factor of 4. It is being stretched farther away from the y-axis. Note, while this may look like a horizontal translation, it is not. The x-intercept changes not because the graph was shifted but because the input values are being moved four times as far away from the y-axis.