Bài 3:
a) Ta có: \(-3x\left(x-2\right)+\left(x-1\right)\left(x+2\right)+2x^2\)
\(=-3x^2+6x+x^2+x-2+2x^2\)
=7x-2
c) Ta có: \(\left(3x+2\right)\left(x-3\right)-\left(x-1\right)\left(2-3x\right)-6x\left(x-1\right)\)
\(=3x^2-9x+2x-6-\left(2x-3x^2-2+3x\right)-6x^2+6x\)
\(=-3x^2-x-6+3x^2-5x+2\)
=-6x-4
Bài 4:
a) Ta có: \(\left(3x-5\right)\left(3x+1\right)-3x\left(3x+2\right)\)
\(=9x^2+3x-15x-5-9x^2-6x\)
\(=-18x-5\)
c) Ta có: \(3x\left(2x-8\right)+\left(6x+1\right)\left(7-x\right)\)
\(=6x^2-24x+42x-6x^2+7-x\)
\(=17x+7\)
Bài 1:
a) Ta có: \(2x\left(1-x\right)+x\left(2x-3\right)\)
\(=2x-2x^2+2x^2-3x\)
=-x
b) Ta có: \(3x\left(2x-5\right)-2x\left(3x-4\right)\)
\(=6x^2-15x-6x^2+8x\)
=-7x
