Q. 54.4( 142 Votes )
In an A.P., if pth term is and qth term is, prove that the sum of first pq terms is 1/2 (pq +1), where p q.
Let tn = nth tern of AP
tn = a + (n – 1)d
Sn = sum of n terms of AP
Let a be the first term and d common difference.
Given, in an AP
pth term = 1/q
qth term = 1/p
(I) – (II)
Putting value of d in (I)
Thus, the sum of the first pq terms of the A.P. is .
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