F(x)=x^2+3x. G(x)=2x-1

Question

(f°g)(3) is the problem im stuck on, Help please.

Answer 1

Hi Yesenia:

 

with a function f(x) or g(x), etc.,

it means take whatever is in the parenthesis of

the function and do the following to it.

Example:  f(x) = 2x³ - 7

               f(x+5) = 2(x+5)³ - 7

 

For your problem:

f(x) = x² + 3x

g(x) = 2x-1

 

(fog)(x) = f(g(x)) = f(2x-1)

 

= (2x-1)² + 3(2x-1)

 

= 4x² - 4x + 1 + 6x - 3

 

= 4x² + 2x - 2

 

Do you understand?