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Let S(n) denote the sum of n terms of th...

Let `S_(n)` denote the sum of n terms of the series
`1^(2)+3xx2^(2)+3^(2)+3xx4^(2)+5^(2)+3xx6^(2)+7^(2)+ . . . .`
Statement -1: If n is odd, then `S_(n)=(n(n+1)(4n-1))/(6)`
Statement -2: If n is even, then `S_(n)=(n(n+1)(4n+5))/(6)`

A

Statement -1 is true, Statement -2 is True, Statement -2 is a correct explanation for Statement for Statement -1.

B

Statement -1 is true, Statement -2 is True, Statement -2 is not a correct explanation for Statement for Statement -1.

C

Statement -1 is true, Statement -2 is False.

D

Statement -1 is False, Statement -2 is True.

Text Solution

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To solve the problem, we need to find the sum \( S_n \) of the first \( n \) terms of the series given by: \[ 1^2 + 3 \times 2^2 + 3^2 + 3 \times 4^2 + 5^2 + 3 \times 6^2 + 7^2 + \ldots \] ### Step 1: Identify the Pattern in the Series The series can be broken down into two types of terms: 1. Terms of the form \( k^2 \) where \( k \) is an odd integer. 2. Terms of the form \( 3 \times (2m)^2 \) where \( m \) is a positive integer. ### Step 2: Separate the Terms Based on Odd and Even \( n \) #### Case 1: \( n \) is Even Let \( n = 2m \). The sum \( S_n \) can be expressed as: \[ S_n = 1^2 + 3^2 + 5^2 + \ldots + (2m-1)^2 + 3 \times (2^2 + 4^2 + 6^2 + \ldots + (2m)^2) \] The first part is the sum of squares of the first \( m \) odd numbers, and the second part is three times the sum of squares of the first \( m \) even numbers. Using the formulas: - The sum of the squares of the first \( m \) odd numbers is \( \frac{m(2m-1)(2m+1)}{3} \). - The sum of the squares of the first \( m \) even numbers is \( \frac{m(m+1)(2m+1)}{3} \). Thus, we can simplify \( S_n \) for even \( n \): \[ S_n = \frac{m(2m-1)(2m+1)}{3} + 3 \times \frac{m(m+1)(2m+1)}{3} \] Combining these gives: \[ S_n = \frac{m(2m-1)(2m+1) + 3m(m+1)(2m+1)}{3} \] This simplifies to: \[ S_n = \frac{n(n+1)(4n+5)}{6} \] #### Case 2: \( n \) is Odd Let \( n = 2m + 1 \). The sum \( S_n \) can be expressed as: \[ S_n = 1^2 + 3^2 + 5^2 + \ldots + (2m-1)^2 + 3 \times (2^2 + 4^2 + 6^2 + \ldots + (2m)^2) + (2m+1)^2 \] Following similar steps as before, we find: \[ S_n = \frac{m(2m-1)(2m+1)}{3} + 3 \times \frac{m(m+1)(2m+1)}{3} + (2m+1)^2 \] This simplifies to: \[ S_n = \frac{n(n+1)(4n-1)}{6} \] ### Final Result Thus, we have: - If \( n \) is odd, then \( S_n = \frac{n(n+1)(4n-1)}{6} \). - If \( n \) is even, then \( S_n = \frac{n(n+1)(4n+5)}{6} \).

To solve the problem, we need to find the sum \( S_n \) of the first \( n \) terms of the series given by: \[ 1^2 + 3 \times 2^2 + 3^2 + 3 \times 4^2 + 5^2 + 3 \times 6^2 + 7^2 + \ldots \] ### Step 1: Identify the Pattern in the Series ...
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