Question

make u the subject of the formula f=uv/u+v

Answer 1

dude this one is really easy,

f = uv/(u+v)
1/f = 1/u + 1/v
u/f = 1 + u/v
uv/f = v + u
u(v/f - 1) = v
u = v/(v/f - 1)
= v / [(v-f)/f]
= vf/(v-f)