If the ratio of the sums of first n terms of two A.P.'s is (7n + 1): (4n + 27), find the ratio of their 9th
terms.
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Let the first terms and the common differences of the two AP be A, a ans D, d.
Their 9th terms are:
⇒A+(9-1)D = A+8D --------------------(i)
⇒a+(9-1)d = a+8d---------------------(ii)
A/Q:
⇒
⇒ (Since the number of terms in both AP is n)
⇒ (Dividing the num and deno in LHS by 2)
⇒ -----------------------------------(iii)
Putting n=17 in --(iii)
⇒
⇒
⇒
Using previously formed equation (i) and (ii) we get that the ratio of their 9th terms
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