Rearrange 1/u + 1/v = 1/f
to make u the subject of the formula. Give your answer in its simplest form.
There are a number of ways to approach this problem.
By subtracting 1/v on both sides we get 1/u as the subject of the equation:
1/u = 1/f - 1/v
The inverse of the equation can be found to make the subject u:
u = 1/(1/f - 1/v)
This can be simplified by multiplying by fv/fv:
u(fv/fv) = fv/(fv/f - fv/v)
As fv/fv is equal to one, this can be simplified further to give the final answer:
u = fv/(v-f)