题目内容
先化简,再求值.
(1)2(x2y+xy)-3(x2y-xy)-4x2y,其中x=1,y=-1.
(2)(xy-
y-
)-(xy-
x+1),其中x=
,y=
.
(1)2(x2y+xy)-3(x2y-xy)-4x2y,其中x=1,y=-1.
(2)(xy-
3 |
2 |
1 |
2 |
3 |
2 |
10 |
3 |
8 |
3 |
(1)原式=2x2y+2xy-3x2y+3xy-4x2y
=-5x2y+5xy,
当x=1,y=-1时,原式=5-5=0;
(2)原式=xy-
y-
-xy+
x-1
=
x-
y-
,
当x=
,y=
时,原式=5-4-
=-
.
=-5x2y+5xy,
当x=1,y=-1时,原式=5-5=0;
(2)原式=xy-
3 |
2 |
1 |
2 |
3 |
2 |
=
3 |
2 |
3 |
2 |
3 |
2 |
当x=
10 |
3 |
8 |
3 |
3 |
2 |
1 |
2 |
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