Find the composition

Question

If f(x)=7x²+5x and g(x)=3x, Find (f  ° g) (x)

 

 

 

 

 

 

( the answer is 63x²+15x but i need help step by step on how they got this)

Answer 1

Cathryn, f(3) would mean plugging in 3 for every x. Instead, we are going to plug in g(x) for every x.

 

Since g(x) = 3x, then (f°g)(x) = 7(3x)² + 5(3x)

 

7(9x²) + 15x = 63x² + 15x

 

Hope this helps!