问题 解答题
已知
M
x2-y2
=
2xy-y2
x2-y2
+
x-y
x+y
,则M=______.
答案

M
x2-y2
=
2xy-y2
x2-y2
+
(x-y)2
x2-y2

M
x2-y2
=
2xy-y2+x2-2xy+y2
x2-y2

M
x2-y2
=
x2
x2-y2

∴M=x2

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