### Home > A2C > Chapter 7 > Lesson 7.1.5 > Problem 7-85

7-85.

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

*f*(*a* + *b*) = 2*a*^{2} + 4*ab* + 2*b*^{2} − 4

*f*(*g*(*x*)) = 10*x*^{2} − 17