Question

What is the 10th term in the sequence below? -1, 1, 3, ... Write your answer as a number.

Answer 1

We notice that the difference between the 2nd term & the first is equal to the difference of the 3rd with the second:

1-(-1) = (3-1) = 2 . So d (common difference ) =2

This is an arithmetic progression with first tem a₁ = (-1) & d =2

Calculating the nth term: Last term = a₁ + (n-1)d
10th term = (-1) + (10-1)(2)= -1 +(9x2) =17

Answer 2

-1 plus 2 equals 1. 1 plus 2 equals 3....