If the pth term of an A.P is 
and the qth term is 
, prove that the sum of the first pq terms must be 
(pq + 1).
If the pth term of an A.P is and the qth term is , prove that the sum of the first pq terms must be (pq + 1).
and the qth term is , prove that the sum of the first pq terms must be (pq + 1).
tp = a + (p-1)d =
……….(1)
tq = a + (q-1)d = 
……….(2)
(1) - (2)
a + (p-1)d =
a + (q-1)d =
---------------------
(p - q)d = 
----------------------
d = 
= 
a + (p-1) =
a = -
= 
=
Sum of the 1st pq terms = 
]
= 
=
Spq =
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