00:01
This question wants me to find the sum of the first 50 terms over the arithmetic sequence, whose general term is given by a sub n equals 5n minus 1.
00:10
Now i know the difference here is going to be 5.
00:15
Let's find the first term.
00:16
So a sub 1 equals 5 times 1 minus 1 is going to be 4.
00:23
So let's look at the formula.
00:26
I'm going to have n divided by 2, 2 times my first term, plus.
00:31
Plus n minus 1 times my difference.
00:36
Now, i know that my first thing i'm going to find is n.
00:41
And since i want the first 50 terms, my n is going to be 50.
00:47
I know my first term is going to be 4...