Find an equation for the nth term of the arithmetic sequence. -1, 2, 5, 8, ...

Question

A. an = -1 + 3(n)
B. an = -1 + 3(n - 1)
C. an = -1 + 3
D. an = -1 + 3(n + 1)

Answer 1

Given a₁ = -1

The common difference is 3

When we get to the nth term we will have added

3 to a₁ a total of n-1 times:

a_n = -1 + 3(n-1)

 

Check:  a₄ = -1 + 3(4-1) = -1+9 = 8