Question

R(r1+r2)=r1r2 solve for R

Answer 1

Hint, divide \(r_1+r_2\) from both sides.

Answer 2

i know i have to that by r1+r2 then canceal out or is R=r1r2 over r1+r2

Answer 3

but do * not by.....

Answer 4

Huh? That's correct, so your final expression is:
\[
R=\frac{r_1r_2}{r_1+r_2}, r_1\ne-r_2
\]