Lời giải:
`a) A=(x-1)(2x-5)-(x+3)(x-2)`
`A=(2x^2-5x-2x+5)-(x^2-2x+3x-6)`
`A=(2x^2-7x+5)-(x^2+x+6)`
`A=2x^2-7x+5-x^2-x+6`
`A=x^2-8x+11`
`b) B=(2x-3)^2+(2x-1)(2x+1)`
`B=4x^2-12x+9+4x^2-1`
`B=-12x+8`
`c) C=(x-2)^3-2x(x-1)(x+1)`
`C=x^3-6x^2+12x-8-2x(x^2-1)`
`C=x^3-6x^2+12x-8-2x^3+2x`
`C=-x^3-6x^2+14x-8`