y' = limit 5/(x + h) - 5/x / h where h is a small increase in x
= 5x - 5x - 5h / xh(x + h)
= -5h / xh(x+ h)
= -5 / x^2 + hx
As h approaches zero hx approaches 0
so y' = limit of -5 (x^2 + hx) = -5 / x^2 (answer)
