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Question
Find the sum to n terms of the A.P., whose kth term is 5k + 1.
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Solution
It is given that the kth term of the A.P. is 5k + 1.
kth term = ak = a + (k – 1)d
∴ a + (k – 1)d = 5k + 1
a + kd – d = 5k + 1
Comparing the coefficient of k, we obtain d = 5
a – d = 1
⇒ a – 5 = 1
⇒ a = 6
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