4-12(x-y)+9(x-y)的平方完全平方公式怎么求得如题

问题描述:

4-12(x-y)+9(x-y)的平方完全平方公式怎么求得如题

4-12(x-y)+9(x-y)^2 =2^2-2*2*3(x-y)+[3(x-y)]^2 =[2-3(x-y)]^2=(3y-3x+2)^2