00:01
Our first goal is to prove n equals 1.
00:05
For our n equals 1 case, so we have 1 squared is equal to n, which is 1, times n plus 1, so 1 plus 1, times 2n plus 1.
00:21
On top, all divided by 6.
00:25
So 1 squared is just 1.
00:28
And on top, we have 1 times 1 plus 1 or 2, times 2 times 1 plus 1 plus 1, or 3.
00:37
So 1 times 2 times 3, all divided by 6, which is just 6 over 6, or 1.
00:47
So that proves our n equals 1 case.
00:56
Now for n equals 2, we have 1 squared plus 2 squared is equal to n or 2 times 2 plus 1, times 2 plus 1, all divided by 6.
01:14
So on the left -hand side, we got 1 plus 4.
01:22
On the right -hand side, we got 2 times 3, times 5, all divided by 6.
01:34
And then we solve both sides, 1 plus 4 are pretty easy.
01:39
5...