For this question, I need to express these two sums as a single sum. Here is what I have so far. I'm not sure if I'm doing it right, can anyone please help me?

$$ \Biggl(3\sum \limits\_{k=1}^{n} (k^2-1)\Biggl) + \Biggl(5\sum\limits\_{k=n+1}^{2n} (k-n)^2+1\Biggl)$$

$$ = \Biggl(3\sum \limits\_{k=n+1}^{2n} (k^2-1)+n\Biggl) + \Biggl(5\sum\limits\_{k=n+1}^{2n} (k-n)^2+1\Biggl)$$

$$ = \Biggl(\sum \limits\_{k=n+1}^{2n} 3(k^2-1)+n + 5(k-n)^2+1\Biggl)$$