1.a²-b²-2b-12.(a-b)²+4ab3.(x+y)²-4(x+y-1)

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1.a²-b²-2b-12.(a-b)²+4ab3.(x+y)²-4(x+y-1)

1.a²-b²-2b-12.(a-b)²+4ab3.(x+y)²-4(x+y-1)
1.a²-b²-2b-1
2.(a-b)²+4ab
3.(x+y)²-4(x+y-1)

1.a²-b²-2b-12.(a-b)²+4ab3.(x+y)²-4(x+y-1)
a²-b²-2b-1
=a²-(b+1)²
=(a-b-1)(a+b+1)
(a-b)²+4ab
=a²+2ab+b²
=(a+b)²
(x+y)²-4(x+y-1)
=(x+y)²-4(x+y)+4
=(x+y+2)²

a²-b²-2b-1
=a²-(b+1)²
=(a-b-1)(a+b+1)
(a-b)²+4ab
=a²+2ab+b²
=(a+b)²
(x+y)²-4(x+y-1)
=(x+y)²-4(x+y)+4
=(x+y+2)²
hhe

1、原式=a²-1-(b²+2b)=a²-(b²+2b+1)=a²-(b-1)²=(a+b-1)(a-b+1)
2、原式=a²-2ab+b²+4ab=a²+2ab+b²=(a+b)²
3、原式=(x+y)²-4x-4y+4=(x+y)²-4(x+y)+2...

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1、原式=a²-1-(b²+2b)=a²-(b²+2b+1)=a²-(b-1)²=(a+b-1)(a-b+1)
2、原式=a²-2ab+b²+4ab=a²+2ab+b²=(a+b)²
3、原式=(x+y)²-4x-4y+4=(x+y)²-4(x+y)+2²=(x+y-2)²
注:第三题最后一步,利用完全平方公式,这里把(x+y)整体认知

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