A1 = 5

an = an-1 (3)

what is the 3rd term of this sequence?

45

Step-by-step explanation:

If a (1) = 5, then a (2) = a (1) * 3, or 5*3, or 15.

If a (2) = 15, then a (3) = a (2) * 3, or a (3) = 15*3 = 45

This is a geometric sequence with first term a (1) = 5 and common ratio 3. We can immediately write the explicit formula

a (n) = 5*3^ (n - 1), which correctly predicts that a (3) = 5*3^ (3 - 1) = 5*9 = 45