求值,过程。
1个回答
2013-02-18
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原式 = [x^2 + y^2 - (x^2 - 2xy+ y^2) + 2xy - 2y^2] / 4y
= [ x^2 + y^2 - x^2 + 2xy - y^2 + 2xy - 2y^2] / 4y
= ( 4xy - - 2y^2 ) / 4y
= 2y (2x - y ) / 4y
= (2x - y ) / 2
= 10 / 2
= 5
= [ x^2 + y^2 - x^2 + 2xy - y^2 + 2xy - 2y^2] / 4y
= ( 4xy - - 2y^2 ) / 4y
= 2y (2x - y ) / 4y
= (2x - y ) / 2
= 10 / 2
= 5
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