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

Asked by Pragya Singh | 1 year ago |  84

##### Solution :-

Given, the kth term of the A.P. is 5k + 1.

kth term = ak = a + (k – 1)d

And,

a + (k – 1)d = 5k + 1

a + kd – d = 5k + 1

On comparing the coefficient of k, we get d = 5

a – d = 1

a – 5 = 1

⇒ a = 6

$$\dfrac{n}{2}[2a+(n-1)d]$$

$$\dfrac{n}{2}[2(6)+(n-1)(5)]$$

$$\dfrac{n}{2}[12+5n-5]$$

$$\dfrac{n}{2}(5n+7)$$

Answered by Abhisek | 1 year ago

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