作业帮1.3xy-4xy-(-2xy)2.- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)3.(-x+2x²+5)+(4x²-3-6x)4.(3a²-ab-+7)-(-4a²+2ab+7)
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1.3xy-4xy-(-2xy)2.- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)3.(-x+2x²+5)+(4x²-3-6x)4.(3a²-ab-+7)-(-4a²+2ab+7)
1.3xy-4xy-(-2xy)
2.- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)
3.(-x+2x²+5)+(4x²-3-6x)
4.(3a²-ab-+7)-(-4a²+2ab+7)
1.3xy-4xy-(-2xy)2.- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)3.(-x+2x²+5)+(4x²-3-6x)4.(3a²-ab-+7)-(-4a²+2ab+7)
1.3xy-4xy-(-2xy)=-xy+2xy=xy
2.- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)
=1/3 a²-1/4a²-1/3ab+2/3ab
=1/12a²+1/3ab
3.(-x+2x²+5)+(4x²-3-6x)
=2x²-x+5+4x²-6x-3
=6x²-7x+2
4.(3a²-ab+7)-(-4a²+2ab+7)
=3a²-ab+7+4a²-2ab-7
=7a²-3ab
1.
3xy-4xy-(-2xy)
=3xy-4xy+2xy
=xy
2.
- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)
=(-1/3+2/3)ab+(-1/4+1/3)a²
=(1/3)ab+1/12a²
3.
(-x+2x...
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1.
3xy-4xy-(-2xy)
=3xy-4xy+2xy
=xy
2.
- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)
=(-1/3+2/3)ab+(-1/4+1/3)a²
=(1/3)ab+1/12a²
3.
(-x+2x²+5)+(4x²-3-6x)
=(2+4)x²+(-1-6)x+(5-3)
=6x²-7x+2
4.
(3a²-ab-7)-(-4a²+2ab+7)
=(3+4)a²+(-1-2)ab+(-7-7)
=7a²-3ab-14
收起
1.xy
2.1/12a²+1/3ab
3.6x²-7x+5
第4题前的7，是+还是-啊？？
+：7a²-3ab
-：7a²-3ab-14
望采纳哈！！
1.原式=3xy-4xy+2xy=(3-4+2)xy=xy
2.原式=- 1/3 ab- 1/4 a²+ 1/3 a²+2/3ab=(-1/3+2/3)ab+(-1/4+1/3)a²
=1/3ab+1/12a²
3....
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1.原式=3xy-4xy+2xy=(3-4+2)xy=xy
2.原式=- 1/3 ab- 1/4 a²+ 1/3 a²+2/3ab=(-1/3+2/3)ab+(-1/4+1/3)a²
=1/3ab+1/12a²
3.原式=-x-6x+2x²+4x²+5-3=6x²-7x+2
4.原式=3a²-ab-+7+4a²-2ab-7=3a²+4a²-ab-2ab+7-7=7a²-3ab
收起
1、 3xy-4xy-(-2xy)= 3xy-4xy+2xy=xy
2、- 1/3 ab- 1/4 a²+ 1/3 a²-(-2/3ab)=- 1/3 ab- 1/4 a²+ 1/3 a²+2/3ab=1/12 a²+1/3ab
3、 (-x+2x²+5)+(4x²-3-6x)=6x²-7x+2
4、 (3a²-ab-+7)-(-4a²+2ab+7)=7a²-3ab-14