### Home > CCA2 > Chapter 6 > Lesson 6.1.5 > Problem6-87

6-87.

Given $f(x)=2x^2−4$ and $g(x)=5x+3$, find the value of each expression below.

Substitute the quantity inside the parentheses ( ) for x into the $f(x)$ or $g(x)$ equation and simplify.

1. $f(a)$

2. $f(3a)$

3. $f(a+b)$

$f(a+b)=2a^2+4ab+2b^2−4$

4. $f(x+7)$

5. $f(5x+3)$

6. $g(f(x))$

$f(g(x))=10x^2−17$