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Read the statements carefully and select...

Read the statements carefully and select the correct option.
Statement-I : The sum of first n terms of an A.P. whose first term is A, the second term is B and the last term is L , is equal to `(( B + L -2A ) ( A + L) )/( 2 ( B - A) )`
Statement-II : If the sum of p terms of an A.P. is equal to the sum of its q terms, then the sum of its `(p + q)` terms is `p + q`.

A

Both Statement-I and Statement-II are false.

B

Both Statement-I and Statement-II are true.

C

Statement-I is true but Statement-II is false.

D

Statement-I is false but Statement-II is true.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the two statements provided and determine their validity. ### Step-by-Step Solution: **Statement I:** The sum of the first \( n \) terms of an A.P. whose first term is \( A \), the second term is \( B \), and the last term is \( L \) is given by: \[ S_n = \frac{(B + L - 2A)(A + L)}{2(B - A)} \] 1. **Identify the first term and common difference:** - First term \( a = A \) - Second term \( b = B \) - Common difference \( d = B - A \) 2. **Identify the last term:** - The last term \( L \) can be expressed in terms of \( n \): \[ L = A + (n-1)d = A + (n-1)(B - A) \] 3. **Express \( n \) in terms of \( A \), \( B \), and \( L \):** - Rearranging gives: \[ L - A = (n-1)(B - A) \implies n = \frac{(L - A)}{(B - A)} + 1 \] 4. **Sum of the first \( n \) terms formula:** - The sum of the first \( n \) terms of an A.P. is given by: \[ S_n = \frac{n}{2} \times \text{(first term + last term)} = \frac{n}{2} \times (A + L) \] 5. **Substituting \( n \):** - Substitute \( n \) into the sum formula: \[ S_n = \frac{(L - A + (B - A))}{2(B - A)} \times (A + L) \] 6. **Simplifying the expression:** - After simplification, we find that the expression matches the one given in Statement I. **Conclusion for Statement I:** - Statement I is **True**. --- **Statement II:** If the sum of \( p \) terms of an A.P. is equal to the sum of its \( q \) terms, then the sum of its \( (p + q) \) terms is \( p + q \). 1. **Using the sum formula for \( p \) and \( q \):** - The sum of the first \( p \) terms: \[ S_p = \frac{p}{2}(2A + (p-1)d) \] - The sum of the first \( q \) terms: \[ S_q = \frac{q}{2}(2A + (q-1)d) \] 2. **Setting the sums equal:** - According to the statement: \[ S_p = S_q \implies \frac{p}{2}(2A + (p-1)d) = \frac{q}{2}(2A + (q-1)d) \] 3. **Solving the equation:** - Simplifying gives a relationship between \( p \) and \( q \) that does not lead to \( S_{p+q} = p + q \). 4. **Calculating \( S_{p+q} \):** - The sum of the first \( p + q \) terms: \[ S_{p+q} = \frac{(p+q)}{2}(2A + (p + q - 1)d) \] - This expression does not simplify to \( p + q \). **Conclusion for Statement II:** - Statement II is **False**. --- ### Final Conclusion: - **Statement I is True.** - **Statement II is False.**
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