Possible Duplicate:
Solving a literal equation containing fractions.
1/R=(1/R1)+(1/R2) solve for R1. I can't figure out what to do, I always end up where I have to either get rid of R1 or an answer that doesn't work when plugging it back in.
Possible Duplicate:
Solving a literal equation containing fractions.
1/R=(1/R1)+(1/R2) solve for R1. I can't figure out what to do, I always end up where I have to either get rid of R1 or an answer that doesn't work when plugging it back in.
Hint:
1) isolate 1/R1
2) simplify both sides of that isolation
3) figure out the two conditions for this to work
If this is not clear, ask again.
$ \frac{1}{R}= \frac{1}{R_1} +\frac{1}{R_2} $
$ \frac{1}{R_1}=\frac{1}{R}-\frac{1}{R_2} $
$ R_1=\frac{1}{\frac{1}{R}-\frac{1}{R_2}} = \frac{1}{\frac{R_2-R}{R\, R_2}}= \frac{R\, R_2}{R_2-R} . $