kak tolong bantu no 4 -6

4. f(x) = x - 5 ,g(x) = x^2 + 1
( f . g)(x) = f(x) . g(x)
= (x-5)(x^2+1)
= x.x^2 - 5.x^2 + 1.x - 5.1
= x^3 - 5x^2 + x -5

5. f(x) = x^2 - 4 ,g(x) = x+2
(f/g)(x) = f(x)/g(x)
= x^2 -4/x+2
= (x+2)(x-2) / (x+2)
= x-2

6. g(x) = x^2 - 9
gof(x) = 4x^2 +12x
g(f(x)) = 4x^2 + 12x
(f(x))^2 - 9 = 4x^2 +12x
f(x)^2 = 4x^2 +12x +9
f(x) = √4x^2+12x+9
f(x) = 2x +3