麻烦大家帮我看下数学题对么?计算 1.(1) -1/3ab-1/4a^2+1/3a^2-(-2/3ab) =-1/3ab-1/4^2+1/3a^2+2/3ab =-1/3ab+2/3ab-1/4a^2+1/3a^2 这里的1/4a^2+1/3a^2在后面我给通分了 =1/3ab-7/12^2 (2) (-x+2x^2+5)+(4x^2-3-6x) =-x+2x^2+5-4x^23+6x =6x

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麻烦大家帮我看下数学题对么?计算1.(1)-1/3ab-1/4a^2+1/3a^2-(-2/3ab)=-1/3ab-1/4^2+1/3a^2+2/3ab=-1/3ab+2/3ab-1/4a^2+1/3

麻烦大家帮我看下数学题对么?计算 1.(1) -1/3ab-1/4a^2+1/3a^2-(-2/3ab) =-1/3ab-1/4^2+1/3a^2+2/3ab =-1/3ab+2/3ab-1/4a^2+1/3a^2 这里的1/4a^2+1/3a^2在后面我给通分了 =1/3ab-7/12^2 (2) (-x+2x^2+5)+(4x^2-3-6x) =-x+2x^2+5-4x^23+6x =6x
麻烦大家帮我看下数学题对么?
计算
1.(1)
-1/3ab-1/4a^2+1/3a^2-(-2/3ab)
=-1/3ab-1/4^2+1/3a^2+2/3ab
=-1/3ab+2/3ab-1/4a^2+1/3a^2 这里的1/4a^2+1/3a^2在后面我给通分了
=1/3ab-7/12^2
(2)
(-x+2x^2+5)+(4x^2-3-6x)
=-x+2x^2+5-4x^23+6x
=6x+(-x)-2x^2+4x^2+5+3
=5x-2x^2+8
(3)
(3a^2-ab+7)-(-4a^2+2ab+7)
=3a^2-ab+7+4a^2-2ab-7
=3a^2+4a^2-2ab+ba-7+7
=7a^2-ab
2.先化简 在求值
5(3a^2b-ab^2)-(ab^2+3a^2b)
=15a^b-5ab^2+ab^2-3a^b
=12a^b-4ab^2
当a=1/2,b=1/3
原式=12×(1/2)^2×1/3-4×1/2×(1/3)^2=1-2/9=7/9

麻烦大家帮我看下数学题对么?计算 1.(1) -1/3ab-1/4a^2+1/3a^2-(-2/3ab) =-1/3ab-1/4^2+1/3a^2+2/3ab =-1/3ab+2/3ab-1/4a^2+1/3a^2 这里的1/4a^2+1/3a^2在后面我给通分了 =1/3ab-7/12^2 (2) (-x+2x^2+5)+(4x^2-3-6x) =-x+2x^2+5-4x^23+6x =6x
1.(1)1/3ab-1/4a^2+1/3a^2-(-2/3ab)=1/3ab+1/12a^2(不是7/12)
(2)你是按照两个式子相减计算的
(-x+2x^2+5)+(4x^2-3-6x) =6x^2-7x+2
(3)(3a^2-ab+7)-(-4a^2+2ab+7) =7a^2-3ab (不是ab)
2.5(3a^2b-ab^2)-(ab^2+3a^2b) =12a^2b-6ab^2 (不是4ab^2)
a=1/2,b=1/3时,原式=2/3