Chad, I am not really sure on your g(x) for the square root, it could be sqrt(x) + 4 or sqrt(x+4) so i will just do in both
F(x) = x^2 - 4x
G(x) = sqrt (x)+4
(F o G)(x) means substitute all x in F(x) with G(x)
(F o G)(x) = (if g(x) = sqrt(x) + 4)
G(x)^2 - 4 x G(x) =
(sqrt (x)+4 )^2 - 4 x (sqrt (x)+4 ) =
x +8sqrt(x) +16 - 4sqrt(x) - 16 =
x + 4 sqrt(x)
(F o G)(x) = (if g(x) = sqrt(x + 4)
G(x)^2 - 4 x G(x) =
(sqrt (x+4)^2 - 4 x (sqrt (x+4) =
sqrt(x +4) - 4sqrt(x+4) =