Question

Answer 1

1. a) \(x\left(x+1\right)\left(7-x\right)=\left(x^2+x\right)\left(7-x\right)=7x^2-x^3+7x-x^2=-x^3+6x^2+7x\)

b) \(\left(2x+1\right)^2+\left(x-5\right)\left(x+5\right)-x\left(5x+7\right)\)

    \(=4x^2+4x+1+x^2-25-5x^2-7x\)

    = \(-3x-24\)

Answer 2

Bài 2.

a) \(=3x\left(x^2-4x+4\right)=3x\left(x-2\right)^2\)

b) \(=\left(3x^2-3y^2\right)-\left(12x-12y\right)=3\left(x-y\right)\left(x+y\right)-12\left(x-y\right)=3\left(x-y\right)\left(x+y-4\right)\)

c) \(=\left(3x^2-5x+3x-5\right)=\left(x+1\right)\left(3x-5\right)\)