Question

Sendo F e G funçoes de dominio Real com F(x)= x² + 2x e G(x)=1-3x, determine:
F(g (x) )= ?

Answer 1

$f(x)=x^{2}+2x\\f(g(x))=[g(x)]^{2}+2g(x)\\f(g(x))=[1-3x]^{2}+2(1-3x)\\f(g(x))=[1^{2}-2*1*3x+(3x)^{2}]+2-6x\\f(g(x))=1-6x +9x^{2}+2-6x\\f(g(x))=3-12x+9x^{2}\\\\\boxed{\boxed{f(g(x))=9x^{2}-12x+3}}$