Chapter 7.2, Problem 8ES

For Exercises 7-12, use the function f given by

$f\left(x\right)=\{\begin{array}{l}x-5,\text{ if <}-\text{6,}\\ {\text{2x}}^2,\text{ if }-\text{ 6 }\le x<-1,\\ \left|x\right|,\text{ if }-\text{1}\le x<10,\\ 3x+1,\text{ if }x\ge 10.\end{array}$

Write the letter of the equation that equation that should be used to find each function value. Letters may be used more than once or not all.

a. $f\left(x\right)=x-5$

b. $f\left(x\right)=2x^2$

c. $f\left(x\right)=\left|x\right|$

d. $f\left(x\right)=3x+1$

$\_\_\_\_\_\_\_f\left(15\right)$