Hello ldx2

Welcome to Math Help Forum!I agree: .

There are various ways of deriving . Here's one. And here's my version:So if we put is the root of the equation:

for which .

Noting that satisfies this equation, we can factorise:

and then discard the factor , since .

We then note that is also a root. Hence is a factor, which again we discard for the same reason; leaving us with the remaining factor:the positive root of which is:Hence

Grandad