Let f(x)=-4x-1 and g(x)=x^2+4. Find (f * g)(5)

Question

Let f(x)=-4x-1 and g(x)=x^2+4. Find (f * g)(5)

Answer 1

Not sure if by f*g you mean the multiplication f(5) times g(5) or the composite function f(g(5)) so I will show you both.  

 

Multiplication: 

f(5) = -4*5 - 1 = -21

g(5) = (5)^2 + 4 = 29

f(5) * g(5) = -21 * 29 = -609 

 

Composition: 

g(5) = (5)^2 + 4 = 29

f(g(5)) = f(29) = -4*29 - 1 = -117