Why isn't 1/f=1/do+1/di just the mathematical equivalent to f=do+di? Can't you raise all terms in the equation to the power of negative 1 to get the latter equation? The maths of reciprocals is confusing me lol.
That is not the lens eqn.
The lens equation is :- 1/f = 1/v - 1/u
Kuzon has written a perfectly acceptable version of the lens equation, one that is commonly used.
Kuzon: raising to a power does not follow a distributive law as does multiplication. So we have a(b + c) = ab + ac but (b + c)2 ≠ b2 + c2.
Sorry, I did not know that version of lens equation; as in our country the lens equation version used is different.