Hard
Find the 9th term of the AP: -1, 4, 9, ...
Explanation
Explanation
The nth term of an AP is aₙ = a + (n-1)d, where a = -1 (first term) and d = 5 (common difference). So the 9th term = -1 + (9-1)(5) = -1 + 40 = 39.
PRO TIP
Re-check your working by substituting the answer back into the original question.