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
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/19 23:04:59
![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](/uploads/image/z/14072888-56-8.jpg?t=%E9%BA%BB%E7%83%A6%E5%A4%A7%E5%AE%B6%E5%B8%AE%E6%88%91%E7%9C%8B%E4%B8%8B%E6%95%B0%E5%AD%A6%E9%A2%98%E5%AF%B9%E4%B9%88%3F%E8%AE%A1%E7%AE%97+1.%281%29+-1%2F3ab-1%2F4a%5E2%2B1%2F3a%5E2-%28-2%2F3ab%29+%3D-1%2F3ab-1%2F4%5E2%2B1%2F3a%5E2%2B2%2F3ab+%3D-1%2F3ab%2B2%2F3ab-1%2F4a%5E2%2B1%2F3a%5E2+%E8%BF%99%E9%87%8C%E7%9A%841%2F4a%5E2%2B1%2F3a%5E2%E5%9C%A8%E5%90%8E%E9%9D%A2%E6%88%91%E7%BB%99%E9%80%9A%E5%88%86%E4%BA%86+%3D1%2F3ab-7%2F12%5E2+%282%29+%28-x%2B2x%5E2%2B5%29%2B%284x%5E2-3-6x%29+%3D-x%2B2x%5E2%2B5-4x%5E23%2B6x+%3D6x)
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