计算(x+y/x-y + 4xy/y2-x2)(x2-9y2)/(x2+2xy-3y2)

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计算(x+y/x-y + 4xy/y2-x2)(x2-9y2)/(x2+2xy-3y2)

计算(x+y/x-y + 4xy/y2-x2)(x2-9y2)/(x2+2xy-3y2)
计算(x+y/x-y + 4xy/y2-x2)(x2-9y2)/(x2+2xy-3y2)

计算(x+y/x-y + 4xy/y2-x2)(x2-9y2)/(x2+2xy-3y2)
(x+y/x-y + 4xy/y2-x2)(x2-9y2)/(x2+2xy-3y2)
=[(x+y/x-y -4xy/(x+y)(x-y)](x+3y)(x-3y)/(x+3y)(x-y).(平方差公式、十字相乘法)
=[(x-y)的平方/(x+y)(x-y)](x+3y)(x-3y)/(x+3y)(x-y).(通分,完全平方公式)
=(x-3y)/(x+y).(约分,化简)