4十12(x一y)+9(x+y)^2

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4十12(x一y)+9(x+y)^2
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4十12(x一y)+9(x+y)^2
4十12(x一y)+9(x+y)^2

4十12(x一y)+9(x+y)^2
=[3(x-y)^2+2]^2+36xy

4十12(x一y)+9(x+y)^2=[3(x+y)-2]²

=9(x+y)²-12(x+y)+4
=[3(x+y)-2]²
详帮助你理可以当(x+y)为一个值z
那么其实就是9z²+4-12z
( 3z-2)²
最后将z带入就的=[3(x+y)-2]²

12x+12y+9x2+2xy+9y2

4+12x-12y+9x^2+18xy+9y^2是不是?

=[3(x+y)-2]²

=9(x+y)²-12(x+y)+4
=[3(x+y)-2]²