, ,

This is a geometric sequence since there is a common ratio between each term. In this case, multiplying the previous term in the sequence by gives the next term. In other words, .

Geometric Sequence:

This is the form of a geometric sequence.

Substitute in the values of and .

Remove parentheses.

Substitute in the value of to find the th term.

Subtract from .

Raise to the power of .

Multiply by .

Find the 4th Term 15 , 45 , 135