1:9（m+n)²-4（2m-n）² =[3(m+n)+2(2m-n)] * [3(m+n)-2(2m-n)] =(7m+n)*(5n-m)2:25(x-y)²-（x+y）²=[5(x-y)+(x+y)]*[5(x-y)-(x+y)]=(6x-4y)*(4x-6y)两题都一样,都是X2 - Y2 =(X+Y)*(X-Y) 的变形...