# Week 1 – Pre Calc 11

In the first week of Pre-Calculus 11 we started unit 1 – Sequences and Series. Something I learned this week was what an arithmetic sequence is and what it does or the purpose of it. In my own definition, an arithmetic sequence is a series of numbers that have the same difference between each number. An example of this would be -3, 0, 3 ,6… is an arithmetic sequence because the difference between each number is 3 and its always 3. The numbers 1, 4, 6, 10… is not an arithmetic sequence because the difference between 1 and 4 is 3 but the difference between 4 and 6 is 2 so it changed and didn’t always have the same difference. We learned this week what an arithmetic sequence is but also what the purpose of it is. If I wanted to know what the 45th term in the series that might be challenging to find out but using the formula $t_n$ = $t_1$ + (n-1)d I can solve and find out the 45th term much easier than I would have if I did all the work and counted by 3, 45 times. After filling in the formula and solving you will get the 45th term in the series which is 129.