一道初中数学分式加减一道分式加减:在1/R=1/R1+1/R2中(1)已知R1,R2求R.(2)已知R,R2求R1一定要有过程

(1) 1/R=1/R1+1/R2=(R1+R2)/(R1*R2)
R=(R1*R2)/(R1+R2)
(2) 1/R1=1/R-1/R2=(R2-R)/(R2*R)
R1=(R2*R)/(R2-R)

很简单呀
(!) R=R1R2/(R1+R2)
(2） R1=RR2/(R2-R)
将求解的未知数放在等式的一边后，具体步骤是通分后求倒就可以了

1/R=（R1+R2）/R1R2 所以R=R1×R2/（R1+R2）
1/R1=1/R - 1/R2 =（R2 - R）/RR2 所以R1=R×R2/（R2 - R）

通分就行了 R=R1R2/(R1+R2)
R1=RR2/(R1-R)

R1=R2*R/(R-R2)
R2=R1*R(R-R1)

fdlkjhytfghjklkljiob n6787898iujkn v4350-98987dh nv

（1）通分1/R=(R1+R2)/R1R2 R=R1R2/(R1+R2)
（2）先移向1/R1=1/R-1/R2再和上面一样通分

已知R1,R2,则
1/R=1/R1+1/R2
1/R=(R1+R2)/R1×R2
R=R1×R2/(R1+R2)
已知R,R2,则
1/R=1/R1+1/R2
1/R1=1/R-1/R2
1/R1=(R2-R)/R×R2
R1=R×R2/(R2-R)

(1)1/R=1/R1+1/R2
1/R=R1/R1R2+R2/R1R2
1/R=(R1+R2)/R1R2
R=R1R2/(R1+R2)
(2)
1/R1=1/R-1/R2
1/R1=R2/RR2-R/RR2
1/R1=(R2-R)/RR2
R1=RR2/(R2-R)

(1):1/R=(R1+R2)R1R2,R=R1R2/(R1+R2)
(2):1/R1=1/R-1/R2,1/R1=(R2-R)R*R2,R1=R*R2/(R2-R)