mn²-m
=m(n²-1)
=m(n+1)(n-1)（1）计算﹙3x²y³﹚²÷﹙﹣2xy﹚²﹙3x²y³﹚²÷﹙﹣2xy﹚²=[(3x²y³)/(-2xy)]²=[(-3/2)xy²]²=9x²y⁴/4