题目内容
化简求值
(1)2x3+4x-
x2-(x+3x2-2x3),其中x=-3.
(2)2(x2y+xy)-3(x2y-xy)-4x2y,其中x=1,y=-1.
(1)2x3+4x-
1 |
3 |
(2)2(x2y+xy)-3(x2y-xy)-4x2y,其中x=1,y=-1.
(1)原式=2x3+4x-
x2-x-3x2+2x3
=4x3+3x-
x2,
当x=-3时,原式=4×(-3)3+3×(-3)-
×(-3)2=-108-9-30=-87;
(2)原式=2x2y+2xy-3x2y+3xy-4x2y
=-5x2y+5xy,
当x=1,y=-1时,原式=-5×12×(-1)+5×1×(-1)=0.
1 |
3 |
=4x3+3x-
10 |
3 |
当x=-3时,原式=4×(-3)3+3×(-3)-
10 |
3 |
(2)原式=2x2y+2xy-3x2y+3xy-4x2y
=-5x2y+5xy,
当x=1,y=-1时,原式=-5×12×(-1)+5×1×(-1)=0.
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