Math Help - Summation regarding variance

1. Summation regarding variance

Hi!
How does one go about the following problem?
(a+1)^2 + (a+2)^2 + (a+3)^2 + ... + (a+n)^2 ?
I am really stuck, so any help will be appreciated! Thanks

2. Originally Posted by Pink Lady
Hi!
How does one go about the following problem?
(a+1)^2 + (a+2)^2 + (a+3)^2 + ... + (a+n)^2 ?
$\sum\limits_{k = 1}^n {\left( {a + k} \right)^2 } = \sum\limits_{k = 1}^n {a^2 } + 2a\sum\limits_{k = 1}^n k + \sum\limits_{k = 1}^n {k^2 }$