00:01
Okay, so we want to show that this is true by induction.
00:04
So p of n is this equation.
00:06
So the first thing we want to do is show that p of 1 is true.
00:09
So if we sub in n equals 1, so the first thing is p of 1.
00:13
If we sub in n equals 1, well, the left -hand side is just 1, and the right -hand side is 1 times 5 times 1 minus 3 over 2.
00:23
And you can see that this is clearly correct because 5 times 1 is 5.
00:27
5 minus 3 is 2, 2 times 1 is 2, 2.
00:31
And 2 divided by 2 is 1.
00:33
So, p of 1 is correct.
00:35
So the next thing we want to do, so this is p of 1.
00:38
The next thing we want to do is assume that it's true for k, and then show that this implies that p of k plus 1 is true.
00:46
Okay, so we're going to let k be some integer, and we suppose that p of k is true.
00:53
So this means that the left -hand side of p of k is just 1 plus 6 plus 11 plus 16 plus dot, dot, dot, dot.
01:02
Plus 5n minus, not 5n of course, 5k minus 4.
01:08
This is the left -hand side of p of k, and the right -hand side is k times 5k minus 3 over 2.
01:19
So we're assuming that this is equal, that both of these sides are equal.
01:27
Okay, so what do we do next? so this is the right -hand side.
01:32
So this is this step.
01:34
So the inductive hypothesis states that the two sides of p of k equal.
01:38
So we know that 1 plus 6 plus 11 plus 16 plus dot dot dot plus 5k minus 4 is equal to k times 5k minus 3 over 2.
01:52
So this is what we know.
01:53
Now we have to show that p of k plus 1 is true.
01:58
Well p of k plus 1 is the following equation.
02:00
It's just 1 plus 6 plus 11 plus 16 plus 16 plus 1.
02:04
Plus dot dot plus 5 times k plus 1 minus 4.
02:12
And the right hand side is just what you get when you plug in k plus 1.
02:15
This is going to be k plus 1 times 5 k plus 1 minus 3 over 2...