Question

if T equals 1 / r + 1 / s equals r + S over RS, then what is 1 / T in terms of R&S?

Answer 1

$T=\dfrac{1}{r}+\dfrac{1}{s}\\\\T=\dfrac{1\cdot s}{r\cdor s}+\dfrac{1\cdot r}{r\cdot s}\\\\T=\dfrac{s}{rs}+\dfrac{r}{rs}\\\\T=\dfrac{s+r}{rs}\to\dfrac{1}{T}=\dfrac{rs}{s+r}$