(x+1)(x-2)-(2x-1)乘x
=x²-x-2-2x²+x
=-x²-2已知(3x+1)(x-1)-(x+3)(5x-6)=m,则m等于m=(3x+1)(x-1)-(x+3)(5x-6)=3x²-2x-1-(5x²+9x-18)=3x²-2x-1-5x²-9x+18=-2x²-11x+17计算:(x-5y)(3x+4y)= = =......(x-5y)(3x+4y)=3x²-11xy-20y²请不要追问了，我睡了，最好采纳吧