问题
解答题
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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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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.