Learning functions, need help with some word problems.

(f+g)(x) = f(x) + g(x)

(f+g)(x) = -6*x - 1 + 4*x^2

(f+g)(x) =4x^2 - 6x -1

if you mean (f o g)(x)

if so

( f o g)(x) = f (g(x))

( f o g)(x) = f (4x^2)*******[g(x) = 4*x^2, so i just substitute it]

f(x)= -6x-1 , now just substitute the value of x with 4x^2

f(4x^2)= -6*(4x^2)-1

f(4x^2)= -24x^2-1

( f o g)(x) = -24x^2-1