Question

What is the 30th term of the linear sequence below?
-4,-1,2,5,8

Answer 1

83

Explanation:

a_1 = -4

a_2 = -1

a_2 - a1 = -1 - (-4) = 3

Each new term is 3 added to the previous term.

a_n = a_1 + 3(n - 1)

Test: Let's find the 4th term and see if we get a_4 = 5.

a_4 = a_1 + 3(4 - 1) = -4 + 3(3) = -4 + 9 = 5

We see that the 4th term really is equal to 5.

a_30 = a_1 + 3(30 - 1) = -4 + 3(29) = -4 + 87 = 83