考点:整式的加减—化简求值
专题:
分析:(1)首先去括号,进而合并同类项将已知数据代入求出即可;
(2)首先去括号,进而合并同类项将已知数据代入求出即可;
(3)首先去括号,进而合并同类项即可得出答案;
(4)首先去括号,进而合并同类项将已知数据代入求出即可;
(5)直接合并同类项,进而将已知数据代入求出即可.
解答:解:(1)6xy-3[3y
2-(x
2-2xy)+1],
=6xy-3(3y
2-x
2+2xy+1)
=6xy-9y
2+3x
2-6xy-3
=-9y
2+3x
2-3
将x=-2,y=-
代入原式得:
原式=-9y
2+3x
2-3
=-9×(-
)
2+3×(-2)
2-3
=-1+12-3
=8;
(2)(2x
2-6x-4)-4(-1+x+x
2),
=2x
2-6x-4+4-4x-4x
2=-2x
2-10x
将x=5代入上式得:
原式=-2x
2-10x=-2×5
2-10×5=-100;
(3)2(a
2b+ab
2)-2(a
2b-1)-2ab
2-2,
=2a
2b+2ab
2-2a
2b+2-2ab
2-2,
=0
无论a,b取何值,原式=0;
(4)
(-4x
2-2x-8)-(
x-1),
=-x
2-
x-2-
x+
=-x
2-x-
将x=
代入上式得:
原式=-x
2-x-
=-(
)
2-
-
=-
;
(5)7x
2-5x+3+2x-3x
2-5,
=4x
2-3x-2,
将x=
代入上式得:
原式=4×(
)
2-3×
-2
=1-
-2
=-
.
点评:此题主要考查了整式的加减运算以及化简求值,正确去括号合并同类项是解题关键.