2x(x的2次方-x+1)-x(2x的2次方+2x-3)
=x(x²-2x+2-2x²-2x+3)
=-4x²+5x
=-4x(1/2)²+5x1/2
=-4x1/4+2.5
=1.5
如果本题有什么不明白可以追问,