Question

Find the sum to n terms of the A.P., whose kth term is 5k + 1.
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Answer 1

Answer:

Answer

Ak =a+(k−1)d=5k+1

⇒a+kd−d=5k+1

By compairing, d=5 & a-d=1

a=1+d

a=1+5=6

Sn = n/2 [2a+(n−1)d]

= n/2 [12+(n−1)5]

=n/2 [5n+7]

Answer 2

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