How do I expand (1+x+x²+...+x^(n-1))²?

[Pattielli]

Can you tell me what the following formula will be after it gets expanded ?
$$(1+x+x^2+...+x^n^-^2+x^n^-^1)^2 = ?$$

Thanks a lot,

 

[Muzza]

What's written inside the parantheses is a geometric series. It's equal to (1 - x^(n - 1 + 1)) / (1 - x). Now just square it...

 

[Pattielli]

Thanks a lot,