Question

If the nth term of an Ap is (4n+1),find the sum of the first 15 term of this Ap.Also find the sum of its nth term

Answer 1

hey man this is the solution

Answer 2

Sum of first 15 term of AP is $S_{15}=495$

The sum of its nth term is $S_n=2n^2+3n$

Explanation:

Given that,

The nth term of the AP is (4n+1).

First term of AP, n = 1 is 5

Second term of AP, n = 2 is 9

Common difference, d = 4

The sum of nth term of an ap is given by :

$S_{15}=\dfrac{n}{2}[2a+(n-1)d]$

$S_{15}=\dfrac{15}{2}[2(5)+(15-1)4]$

$S_{15}=495$

The sum of the first 15 term of the AP is 495.

The sum of its nth term of AP is given by :

$S_n=\dfrac{n}{2}(a+a_n)$

$S_n=\dfrac{n}{2}(5+(4n+1))$

$S_n=2n^2+3n$

Hence, this is the required solution.

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Arithmetic Progression

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