let f(x) = 4x + 5 and g(x) = x-5/4, find (f x g) (x) =

Question

let f(x) = 4x + 5 and g(x) = x-5/4, find (f x g) (x)

Answer 1

If I understand you correctly, you are asking about f(g(x)), not f(x) * g(x). If that is so, then consider g(x) to be the ‘x’ in f(x). Then:

f(g(x)) = f(x - 5/4)

= 4(x - 5/4) + 5

= 4x – 5 + 5

= 4x

Answer 2

Multiply f(x) by g(x).  You have both functions.  Just do the algebra.

 

(4x + 5)(x - 5/4) = ?