Hi, well got my exam tomorrow and this is the only topic area I struggle with soo much, a past paper i'm trying here asks this qustion:

It is given that

Use the formulae for

and

to show that

.

I know that I treat the +1 as n but I really dont know where I should take out factors or when I should expand etc. Also I get the formulas for the r squared and r so im aware of what they are.

Each time Ive tried Ive managed to get to either

or

I would be really greatful if someone could explain what process I should do to get the answer.

Thankyou !