Question

Given the sequence (-3, 2, 7, 12,....), find a(25). *HINT: first determine if the

sequence is arithmetic or geometric, find the common difference or ratio
write an equation, plug in 25. *

Answer 1

a(25) = 117

Explanation:

First look at how the given terms behave:

From -3 to 2 is a jump of 5;

From 2 to 7 is a jump of 5;

From 7 to 12 is a jump of 5

Since there is a common difference, this is an arithmetic sequence.

The general formula for an arithmetic sequence is a(n) = a(1) + 5(n - 1).

Thus, a(25) = -3 + 5(25 - 1), or a(25) = -3 + 120, or a(25) = 117