Question

Sabendo que a =x²-6x+12 b=3x²-3x+4 e c =x- 5 ,determine 2a-(b.c)

Answer 1

$2a-(b.c)~=~\\\\\\=~2\,.\,(x^2-6x+12)~-~(3x^2-3x+4)\,.\,(x-5)$

$=~(2\,.\,x^2-2\,.\,6x+2\,~.~\,12)~-~(3x^2\,.\,x~+~3x^2\,.\,(-5)~-~3x\,.\,x~-~3x\,.\,(-5)~+~4\,.\,x~+~4\,.\,(-5))$

$=~(2x^2-12x+24)~-~(3x^3~-~15x^2~-~3x^2~+~15x~+~4x~-~20)\\\\\\=~2x^2-12x+24~-~(3x^3-18x^2+19x-20)\\\\\\=~2x^2-12x+24~-3x^3+18x^2-19x+20\\\\\\=~\boxed{-3x^3+20x^2-31x+44}$