RT= 1/r1 t 1/r2. Transpose the equation for r1.?

Question

I know the answer and how to get it. I Just want see how many others can work the problem.

Answer 1

RT = 1/r1 + 1/r2
= (r2 + r1)/(r1r2)
RTr1r2 = r1 + r2
RTr1r2 - r1 = r2
r1(RTr2 - 1) = r2
r1 = r2 / (RTr2 - 1)

PS. This is basic algebra