化简或求值: (1)化简:(2m-3n+7)-(-6m+5n+2) (2)已知|x+2|+(y-
|
(1)原式=2m-3n+7+6m-5n-2=8m-8n+5;
(2)原式=4xy-x2-5xy+y2+x2+3xy=2xy+y2,
∵|x+2|+(y-
)2=0,∴x+2=0,y-1 2
=0,1 2
解得:x=-2,y=
,1 2
则原式=-2+
=-11 4
.3 4
化简或求值: (1)化简:(2m-3n+7)-(-6m+5n+2) (2)已知|x+2|+(y-
|
(1)原式=2m-3n+7+6m-5n-2=8m-8n+5;
(2)原式=4xy-x2-5xy+y2+x2+3xy=2xy+y2,
∵|x+2|+(y-
)2=0,∴x+2=0,y-1 2
=0,1 2
解得:x=-2,y=
,1 2
则原式=-2+
=-11 4
.3 4