Question 896678
that's what you should be doing as far as i can see.
let me see what i can get and we can compare notes.


you have:


g(x) = x + 1


f(u) = 3u^2 + 3u - 4


to find f(g(x)), you replace u with x+1 and evaluate.


you get:


f(g(x)) = 3(x+1)^2 + 3(x+1) - 4 which becomes:


f(g(x)) = 3(x^2 + 2x + 1) + 3x + 3 - 4 which becomes:


f(g(x)) = 3x^2 + 6x + 3 + 3x + 3 - 4


combine like terms to get:


f(g(x)) = 3x^2 + 9x + 2


that's your solution.


an easy way to check it out is as follows:


let x = 3 (any value of x chosen at random will do)


g(x) = 3+1 = 4


f(4) = 3*4^2 + 3*4 - 4 = 48 + 12 - 4 = 56


now go to your final equation and solve using x = 3


f(g(x)) = 3x^2 + 9x + 2 becomes:


f(g(3)) = 3*3^2 + 9*3 + 2 which becomes:


f(g(3)) = 3*9 + 27 + 2 which becomes:


f(g(3)) = 27 + 27 + 2 which becomes:


f(g(3)) = 56


both the original equations and the final equations give you the same answer so you're good.