Question

F = u*v / u + v make u the subject of this formula

Answer 1

F = u*v / u + v

multiply both sides by u+v.

F(u+v)=u*v

opening bracket

Fu+Fv=u*v

Fu=u*v-Fv

factor out v on the right hand side;

Fu=v(u-F)

dividing both sides by (u-F)

Fu/(u-F)=v

v=Fu/(u-F)