Question

Calculati : a) (x-1)(x+2) +(3x-1)(2x+5) -3x(x+1) b) (x-7)(x+3) -(x+1)(x+2) +(5-x)(x-4)

Answer 1

$a) .(x-1)(x+2) +(3x-1)(2x+5) -3x(x+1)= \\ =x^2+2x-x-2+6x^2+15x-2x-5-3x^2-3x= \\ =4x^2+11x-7 \\ b) .(x-7)(x+3) -(x+1)(x+2) +(5-x)(x-4)= \\ =x^2+3x-7x-21-(x^2+2x+x+2)+5x-20-x^2+4x= \\ =x^2+3x-7x-21-x^2-2x-x-2+5x-20-x^2+4x= \\ =-x^2+2x-43$