Question

A geometric sequence is defined recursively by an = 4an-1. The 10th term of the sequence is a10 = 3.5. What is a13?

Answer 1

geometric sequence \[a_{11}=4a_{10}\\a_{12}=4a_{11}\\a_{13}=4a_{12}\]just calculate step by step if you want, or replace like \[a_{13}=4a_{12}=4(4a_{11})=4(4(4(a_{10})))\]