因式分解：25(x+y)²-9(x-y)²；（x+y）²-4（x+y-1）.急求，谢谢~~

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25(x+y)²-9(x-y)²知逗早
=[5(x+y)-3(x-y)][5(x+y)+3(x-y)]
=(2x+8y)(8x+2y)
=4(x+4y)(4x+y)

（x+y）²搭雀-4（x+y-1）.
=（x+y）指皮²-4（x+y)+4
=(x+y-2)^2

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