问题 解答题
4x2-y2
x2-4y2
-
(2x-y)2
x2-4y2
-
2y2-4xy
4y2-x2
答案

原式=

4x2-y2
x2-4y2
-
(2x-y)2
x2-4y2
+
2y2-4xy
x2-4y2

=

4x2-y2-4x2+4xy-y2+2y2-4xy
x2-4y2

=

0
x2-4y2

=0.

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