I honestly can't figure out how to get this answer, I feel like a complete idiot. I've taken up to Calc 2, so I'm not an idiot just been a while.
I have the problem..
$$(n-1)^2 - \frac {(n-2)(n-1)}{2}$$
The answer is..
$$\frac {(n-1)n}{2}$$
How do I get there??
$$2\frac {(n-1)(n-1)}2 - \frac {(n-2)(n-1)}2 \dots$$
I'm so lost..
You're so close; the step you are missing is:
$$2\frac{(n-1)(n-1)}{2}-\frac{(n-2)(n-1)}{2}=\frac{(n-1)[2(n-1)-(n-2)]}{2}=\frac{(n-1)[2n-2-n+2]}{2}=\ldots$$