Question

Find the nth term of the A.P. 13, 7, 1, –5, –11, ......... . Using it, find its (i) 9th term (ii) 16th term.

Answer 1

Here $$a = 13$$ and $$d = 7 - 13 = -6$$. 

nth term: $$T_n = 13 + (n - 1) \times (-6) = 19 - 6n$$. 

Therefore $$T_9 = 19 - 6 \times 9 = -35$$ and $$T_{16} = 19 - 6 \times 16 = -77$$. 

So nth term = 19 – 6n, 9th term = –35, 16th term = –77.