The common ratio of a geometric sequence is the number that each term of the sequence is multiplied by. This means that the the previous term is multiplied by the common ratio to get the current term. The common ratio can also be used to create a function that can predict future terms.
To find the common ratio of this sequence, divide a term by the previous term. For example, -15/5. This gives the answer, -3. Dividing the terms allows us to figure out what factor is being multiplied by in the sequence.
