用完全平方公式填空:4-12(X-Y)+9(X-Y)^2=______急!它给出的答案是3X-3Y-2..

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用完全平方公式填空:4-12(X-Y)+9(X-Y)^2=______急!
它给出的答案是3X-3Y-2..

因为a^2-2ab+b^2=(a-b)^2
所以4-12(X-Y)+9(X-Y)^2
=2^2-2*2*3(X-Y)+[3(X-Y)]^2
=[2-3(X-Y)]^2
它给出的答案3X-3Y-2是错得

(2-3(x-y))^2

2^2-2*2*3(X-Y)+[3(X-Y)]^2
=[2-3(X-Y)]^2

4-12(X-Y)+9(X-Y)^2
=2^2-2*2*3(X-Y)+[3(X-Y)]^2
=[2-3(X-Y)]^2

4-12(X-Y)+9(X-Y)^2=[3(X-Y)-2]^2

[3(x-y)-2]^2
用x^2-2xy+y^2=(x-y)^2