Work Step by Step
We can see that the quotient of neighbour terms is $-1$ and $a_1=-1$, so $a_n=(-1)^n$ for all $n$ natural numbers.
You can help us out by revising, improving and updating this answer.Update this answer
After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.