令a=2x²-x+1 b=x²-2x+3 则
3x²-3x+4=a+b
所以
原式=4ab-(a+b)²
=4ab-a²-2ab-b²
=-(a²-2ab+b²)
=-(a-b)²
=-(2x²-x+1-x²+2x-3)²
=-(x²+x-2)²
=-(x-1)²(x+2)²