计算(x-y+4xyx-y)(x+y-4xyx+y)的正确结果是( ) A.y2-x2 B.x2-y2 C.(x-y)2x2-y2(x≠y) D.x2-y2x2+y2\;
问题描述:
计算(x-y+
)(x+y-4xy x-y
)的正确结果是( )4xy x+y
A. y2-x2
B. x2-y2
C.
(x≠y)(x-y)2
x2-y2
D.
\;
x2-y2
x2+y2
答
(x-y+
)(x+y-4xy x-y
)4xy x+y
=
•
(x-y)2+4xy x-y
(x+y)2-4xy x+y
=
•(x+y)2 x-y
(x-y)2 x+y
=(x+y)(x-y)=x2-y2,故选B.