the following problem refers to a geometric sequence. If a_1=5 and r=3, find a_n.

a_n=a_1 *r^n-1

Your answer is correct, if you meant

a_n = a_1 * r^(n-1)

Now just plug in your numbers.

To find a_n, we can plug in the given values of a_1 and r into the formula for the nth term of a geometric sequence: a_n = a_1 * r^(n-1).

Given:
a_1 = 5 (the first term)
r = 3 (the common ratio)

Substituting these values into the formula for a_n, we have:
a_n = 5 * 3^(n-1)

This will give us the general expression for a_n in terms of n, which represents the nth term of the geometric sequence.