# Week 2 Pre Calc 11

This week I learned about Finite geometric series, I learned how to find $t_n$ and I also learned how to find the sum of $t_1$ to $t_n$.

To find $t_n$ you need $t_1$ and the common ratio.

So say I was trying to find $t_(15)$, so $t_1$=4 and the common ratio is 3. This is what you would do.

Then to find the sum of all the 15 t’s, you would add $t_1$ + $t_2$ + $t_3$ +…etc. But the easier way to do it would be to do this.