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已知x²-y²=20,求[(x-y)²+4xy][(x+y)²-4xy]的值
1个回答
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[(x-y)²+4xy][(x+y)²-4xy]
=(x^2+y^2+2xy)(x^2+y^2-2xy)
=(x+y)^2(x-y)^2
=(x²-y²)^2
=20^2
=400
=(x^2+y^2+2xy)(x^2+y^2-2xy)
=(x+y)^2(x-y)^2
=(x²-y²)^2
=20^2
=400
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