问题
选择题
下列计算正确的是( )
|
答案
A、原式=
,故本选项错误;y2 x2
B、左边=
=x2-y2 y-x
=-y-x≠右边,故本选项错误;-(y-x)(y+x) y-x
C、左边=
≠右边,故本选项错误;n-m mn
D、左边=
=(a+b)(a-b) (a-b)2
=右边,故本选项正确.a+b a-b
故选D.
下列计算正确的是( )
|
A、原式=
,故本选项错误;y2 x2
B、左边=
=x2-y2 y-x
=-y-x≠右边,故本选项错误;-(y-x)(y+x) y-x
C、左边=
≠右边,故本选项错误;n-m mn
D、左边=
=(a+b)(a-b) (a-b)2
=右边,故本选项正确.a+b a-b
故选D.