The question is about the rule of 72, to determine the accuracy of this rule, I need to follow these steps:

Suppose the effective annual interest rate is x, and the corresponding doubling time is Y1(x). Show that (1+x)^Y1 = 2 and that Y1 (x) = log2/log(1+x)

This is the last question on effective annual interest rates I have, can someone give me a hint?

Thankx

Keith