问题
解答题
化简求值 (x+2y)2-(x+y)(x-y),其中x=-2,y=
|
答案
(x+2y)2-(x+y)(x-y),
=x2+4xy+4y2-x2+y2,
=4xy+5y2,
当x=-2,y=
时,1 2
原式=4×(-2)×
+5×(-1 2
)2=-21 2
.3 4
化简求值 (x+2y)2-(x+y)(x-y),其中x=-2,y=
|
(x+2y)2-(x+y)(x-y),
=x2+4xy+4y2-x2+y2,
=4xy+5y2,
当x=-2,y=
时,1 2
原式=4×(-2)×
+5×(-1 2
)2=-21 2
.3 4