https://www.youtube.com/watch?v=C7tE26CDI2M
https://www.youtube.com/watch?v=0I-uf8TI79E Writing Explicit Formulas for Geometric Sequences:
https://www.youtube.com/watch?v=9jj0Jx9NvNc Writing Recursive and Explicit Formulas for Arithmetic Sequences:
https://www.youtube.com/watch?v=V_UPyzGjFa0