Step-by-step explanation:
f(x)=x^2-4x-9
g(x)=-3x-5
so when f(g(x)) that x is a number
-3x-5 equals the number in f(x) so that x is -3x-5
f(-3x-5) and if f(x)=x^2-4x-9
then inserting in -3x-5 for x in f(x) and distrubute
(-3x-5)^2-4(-3x-5)-9
9x^2+42x+36
I hope that helps :)
Answer:
9x^2 + 42x + 16
Step-by-step explanation:
f(g(x))
Plug in the expression for g(x)
f(g(x)) = f(-3x - 5)
f(x) = x^2 - 4x - 9
For every x in f(x) replace it with -3x - 5
f(-3x - 5) = (-3x - 5)^2 - 4(-3x -5) -9
Expand
f(-3x - 5) = (9x^2 + 30x + 25) + (12x + 20) - 9
Combine like terms
f(-3x - 5) = 9x^2 + 42x + 16
f(g(x)) = 9x^2 + 42x + 16