The 5th and 13th terms of an AP are 5 and –3 respectively. Find the AP and its 30th term.

To Find: AP and its 30th term (i.e. a30=?)


Given: a5=5 and a13=–3


Formula Used: an = a + (n - 1)d


(Where a=a1 is first term, a2 is second term, an is nth term and d is common difference of given AP)


By using the above formula, we have


a5 = 5 = a + (5 - 1)d , and a13 = –3 = a + (13 - 1)d


a + 4d =5 and a + 12d = –3


on solving above 2 equation, we and a + 12d = –3get


a = 9 and d= (–1)


So a30 = 9 + 29(–1) = –20


AP is (9,8,7,6,5,4……) and 30th term = –20


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