Find the 13th term of the geometric sequence 4, -8, 16

Answer 1

ar⁰ is the 1st term. ar¹ is the 2nd term. Note that the term number is always 1 more than the power of r. So ar¹² is the 13th term.

a is the 1st term which is 4. r=ar¹/ar⁰ =-8/4 = -2

So the 13th term is ar¹² = 4*(-2)¹² =4* 4096 = 16,384