# Thread: Express R2 as a function of x

1. ## Express R2 as a function of x

1/R=1/R1+1/R2

The total is 1.2, R1 is x.
I got down to 1/R= R1+R2/R1*R2. But from there I'm lost any pointers? Thanks

Oh and the answer is 1.2x/x-1.2 I don't know how to get there though.

2. $\displaystyle \frac{1}{1.2} = \frac{1}{x} + \frac{1}{R_2}$

$\displaystyle \frac{1}{R_2} = \frac{1}{1.2} - \frac{1}{x}$

$\displaystyle \frac{1}{R_2} = \frac{x - 1.2}{1.2x}$

$\displaystyle R_2 = \frac{1.2x}{x-1.2}$

3. Originally Posted by tukeywilliams
$\displaystyle \frac{1}{1.2} = \frac{1}{x} + \frac{1}{R_2}$

$\displaystyle \frac{1}{R_2} = \frac{1}{1.2} - \frac{1}{x}$

$\displaystyle \frac{1}{R_2} = \frac{x - 1.2}{1.2x}$

$\displaystyle R_2 = \frac{1.2x}{x-1.2}$
how did you get from this part
$\displaystyle \frac{1}{R_2} = \frac{x - 1.2}{1.2x}$
to this part

$\displaystyle R_2 = \frac{1.2x}{x-1.2}$
thank you so much for the help

4. I took the reciprocal.

5. Originally Posted by tukeywilliams
I took the reciprocal.
of course.. man I'm stupid