R1分之1+R2分之1=?（R1分之1）+（R2分之1）=?（12a²分之5）-（8ab分之3）=?｛（x+1）分之（x+2）｝-｛（x+2）分之（x＋1）｝=?｛（a+1）分之（a-1）｝-（a分之1）.｛（a²-4）分之2a｝-｛（a-2）

R1分之1+R2分之1=?（R1分之1）+（R2分之1）=?（12a²分之5）-（8ab分之3）=?｛（x+1）分之（x+2）｝-｛（x+2）分之（x＋1）｝=?｛（a+1）分之（a-1）｝-（a分之1）.｛（a²-4）分之2a｝-｛（a-2）
R1分之1+R2分之1=?
（R1分之1）+（R2分之1）=?
（12a²分之5）-（8ab分之3）=?
｛（x+1）分之（x+2）｝-｛（x+2）分之（x＋1）｝=?
｛（a+1）分之（a-1）｝-（a分之1）.
｛（a²-4）分之2a｝-｛（a-2）分之1）｝
｛（a²-2a）分之（a+2）｝-｛（a²-4）分之（a+4）.
没去上学，生病ing
所以不是很理解题意，弄不清楚，

R1分之1+R2分之1=?（R1分之1）+（R2分之1）=?（12a²分之5）-（8ab分之3）=?｛（x+1）分之（x+2）｝-｛（x+2）分之（x＋1）｝=?｛（a+1）分之（a-1）｝-（a分之1）.｛（a²-4）分之2a｝-｛（a-2）
通分
1/R1 + 1/R2 = R2/R1R2 + R1/R1R2 = (R1+R2) / R1R2
5/12a² - 3/8ab = 5b/12a²b - 3a/8a²b = (5b-3a)/8a²b
(x+2)/(x+1) - (x+1)/(x+2) = (x+2)²/(x+1)(x+2) - (x+1)²/(x+1)(x+2)
= [(x+2)²-(x+1)²] / (x+1)(x+2) = (2x+3)/(x+1)(x+2)
(a-1)/(a+1) - 1/a = (a-1)a/a(a+1) - (a+1)/a(a+1) = (a²+1)/a(a+1)
2a/(a²-4) - 1/(a-2) = 2a / (a-2)(a+2) - (a+2)/(a-2)(a+2) = (a-2)/(a-2)(a+2) = 1/(a+2)
(a+2)/(a²-2a) - (a+4)/(a²-4) = (a+2)/a(a-2) - (a+4)/(a-2)(a+2)
= (a+2)²/a(a-2)(a+2) -(a+4)a / a (a-2)(a+2)
= (a+2)² - a(a+4) / a(a-2)(a+2)
= 4/a(a²-4)
= 4/ a3 -4a

先分母通分，再计算分子。这些题目都不难啊，如果不会通分Hi我。

R1分之1）+（R2分之1）=1/R1+1/R2=(R1+R2)/R1R2
（12a²分之5）-（8ab分之3）=5/12a²-3/8ab=10b/24a²b-9a/24a²b=(10b-9a)/24a²b
｛（x+1）分之（x+2）｝-｛（x+2）分之（x＋1）｝=
(x+2)/(x+1)-(x+1)/(x+2)=[(x...

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R1分之1）+（R2分之1）=1/R1+1/R2=(R1+R2)/R1R2
（12a²分之5）-（8ab分之3）=5/12a²-3/8ab=10b/24a²b-9a/24a²b=(10b-9a)/24a²b
｛（x+1）分之（x+2）｝-｛（x+2）分之（x＋1）｝=
(x+2)/(x+1)-(x+1)/(x+2)=[(x+2)²-(x+1)²]/(x+1)(x+2)=(2x+3)/(x²+3x+2)
｛（a+1）分之（a-1）｝-（a分之1）=(a-1)/(a+1)-1/a=(a²-a-a-1)/a(a+1)=(a²-2a-1)/(a²+a)
｛（a²-4）分之2a｝-｛（a-2）分之1）｝=2a/(a²-4)-1/(a-2)=(2a-a-2)/(a²-4)=(a-2)/(a+2)(a-2)=1/(a+2)
｛（a²-2a）分之（a+2）｝-｛（a²-4）分之（a+4）.
(a+2)/(a²-2a)-(a+4)/(a²-4)=(a+2)²/[a(a²-4)]-(a²+4a)/[a(a²-4)=4/[a(a²-4)]

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1/R1+1/R2
=(R1+R2)/(R1*R2)
5/(12a²)-3/(8ab)
=(10b-39a)/(24a²b)
(x+2)/(x+1)-(x+1)/(x+2)
=1+1/(x+1)-1-1/(x+2)
=1/(x+1)-1/(x+2)
=1/((x+1)(x+2))
(a-1)/(a+1)-1/a

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1/R1+1/R2
=(R1+R2)/(R1*R2)
5/(12a²)-3/(8ab)
=(10b-39a)/(24a²b)
(x+2)/(x+1)-(x+1)/(x+2)
=1+1/(x+1)-1-1/(x+2)
=1/(x+1)-1/(x+2)
=1/((x+1)(x+2))
(a-1)/(a+1)-1/a
=1-2/(a+1)-1/a
=1-(2a+a+1)/(a(a+1))
=1-(3a+1)/(a(a+1))
2a/(a²-4)-1/(a-2)
=2a/((a+2)(a-2))-(a+2)/((a+2)(a-2))
=(2a-a-2)/((a+2)(a-2))
=(a-2)/((a+2)(a-2))
=1/(a+2)
(a+2)/(a²-2a)-(a+4)/(a²-4)
=(a+2)/(a(a-2))-(a+4)/((a+2)(a-2))
=((a+2)²-a(a+4))/(a(a+2)(a-2))
=4/(a(a+2)(a-2))

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所有的都是通过通分，将分母化成一样，然后对分子做运算而得出结果
1/R1+1/R2=(R1+R2)/(R1*R2)
5/12a^2-3/8ab=(10b-9a)/(24a^2*b)
(x+2)/(x+1)-(x+1)/(x+2)=(2x+3)/[(x+1)(x+2)]
(a-1)/(a+1)-1/a=(a^2-2a-1)/[a(a+1)]
2a/(a^2-4...

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所有的都是通过通分，将分母化成一样，然后对分子做运算而得出结果
1/R1+1/R2=(R1+R2)/(R1*R2)
5/12a^2-3/8ab=(10b-9a)/(24a^2*b)
(x+2)/(x+1)-(x+1)/(x+2)=(2x+3)/[(x+1)(x+2)]
(a-1)/(a+1)-1/a=(a^2-2a-1)/[a(a+1)]
2a/(a^2-4)-1/(a-2)=1/(a+2)
(a+2)/(a^2-2a)-(a+4)/(a^2-4)=4/[a(a^2-4)]
如果还有不明白的地方可以来问我

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