Question

If sum to n terms of a series is given by (2n + 7) then its second term will be given by​

Answer 1

Answer:

2

Step-by-step explanation:

Since, sum to n terms is given by (2n + 7),

Sum to 1 terms = 9

Sum to 2 terms = 11

Thus, the 2nd term must be 2.

Answer 2

The second term of the series is 2

Given :

Sum of n terms of a series is given by (2n + 7)

To find :

The second term of the series

Solution :

Solution :Step 1 of 2 :

Write down sum of n terms of the series

Here it is given that sum of n terms of the series is given by (2n + 7)

Let Sₙ = The sum of the first n terms of the series

∴ Sₙ = 2n + 7

Step 2 of 2 :

Find second term of the series

Let aₙ = nth term of the series

The sum of the first 1 term of the series

= S₁

= a₁

= (2 × 1) + 7

= 2 + 7

= 9

∴ a₁ = 9 - - - - - - - (1)

The sum of the first 2 terms of the series

= S₂

= a₁ + a₂

= (2 × 2) + 7

= 4 + 7

= 11

∴ a₁ + a₂ = 11 - - - - - - - (2)

Equation 2 - Equation 1 gives

a₂ = 11 - 9

⇒ a₂ = 2

Hence second term of the series is 2

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