Question

Write a possible explicit rule for the nth term of the sequence, then use it to find the 20th term.

5, -10, 20, -40, 80, -160....

Ans: a(n) = 5(-2)^n - 1
20th term: -2621440

Answer 1

one problem, you should have brackets around n-1

so a(n) = 5(-2)^(n-1)
otherwise, good job