4-12(x-y)+9(x-y)² =(2-3x+3y)²
问题描述：
4-12(x-y)+9(x-y)² =(2-3x+3y)²
答
2²-2(x-y)2+[3(x-y)]²=[2-3(x+y)]²[2-3(x-y)]²=[2-3(x+y)]²2-3(x-y)=2-3(x+y) 2-3(x-y)=3(x+y)-22-3x+3y=2-3x-3y 2-3x+3y=3x+3y-23y+3y=0 -3x-3x=-2-2y=0 -6x=-4