00:01
Okay, these are arithmetic sequences, so each term is obtained by adding 5 to the previous term, so common difference is 5, okay? and this is the first term, this is the nth term, so we need to find the n.
00:18
So the formula is a n is equal to a 1 plus n minus 1 d, so a n is 738, a 1 is 8, and then plus n minus 1 times 5, subtract 8, and divide by 5, n minus 1 is 730, divide by 5, which is 146, okay? and then so n is 147.
00:59
Why is that important? because the first, or the sum of the first n terms of an arithmetic sequence is given by this formula, and we needed that n.
01:17
So now that we know n, 147, a 1 is 8, and a n term is 738 over 2, so this is going to be equal to, okay, okay, so the answer is 54 ,831 for this one, okay? same idea here, if you put 1, you get negative 9, and then plus, put 2, 8 minus 13 is negative 5, and then put 3, 12, negative 1, so you got the idea.
01:58
So now the common distance, common difference d is 4, you know, we need to add plus 4 to get to the next term...