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Let a,b and c be such that (b+c) ne 0 ...

Let a,b and c be such that (b+c) `ne` 0 . If `|(a,a+1,a-1),(-b,b+1,b-1),(c,c-1,c+1)|+|(a+1,b+1,c-1),(a-1, b-1,c+1),((-1)^(n+2)a , (-1)^(n+1)b,(-1)^n c)|=0` , then the value of 'n' is :

A

Zero

B

Any even integer

C

Any odd integer

D

Any integer

Text Solution

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The correct Answer is:
To solve the problem, we need to evaluate the determinants given in the question and find the value of \( n \) such that the sum of these determinants equals zero. ### Step 1: Write down the determinants We have two determinants to consider: 1. \( D_1 = |(a, a+1, a-1), (-b, b+1, b-1), (c, c-1, c+1)| \) 2. \( D_2 = |(a+1, b+1, c-1), (a-1, b-1, c+1), ((-1)^{n+2}a, (-1)^{n+1}b, (-1)^n c)| \) We need to find \( n \) such that: \[ D_1 + D_2 = 0 \] ### Step 2: Evaluate \( D_1 \) To evaluate \( D_1 \), we can use the determinant formula for a 3x3 matrix: \[ D_1 = a \begin{vmatrix} b+1 & b-1 \\ c-1 & c+1 \end{vmatrix} - (a+1) \begin{vmatrix} -b & b-1 \\ c & c+1 \end{vmatrix} + (a-1) \begin{vmatrix} -b & b+1 \\ c & c-1 \end{vmatrix} \] Calculating the minors: - \( \begin{vmatrix} b+1 & b-1 \\ c-1 & c+1 \end{vmatrix} = (b+1)(c+1) - (b-1)(c-1) \) - \( \begin{vmatrix} -b & b-1 \\ c & c+1 \end{vmatrix} = -b(c+1) - (b-1)c \) - \( \begin{vmatrix} -b & b+1 \\ c & c-1 \end{vmatrix} = -b(c-1) - (b+1)c \) After calculating these, we can substitute back into \( D_1 \). ### Step 3: Evaluate \( D_2 \) Similarly, we evaluate \( D_2 \): \[ D_2 = |(a+1, b+1, c-1), (a-1, b-1, c+1), ((-1)^{n+2}a, (-1)^{n+1}b, (-1)^n c)| \] Using the same determinant formula, we can expand this determinant and calculate the minors as we did for \( D_1 \). ### Step 4: Set up the equation After evaluating both determinants, we will have expressions for \( D_1 \) and \( D_2 \). We set up the equation: \[ D_1 + D_2 = 0 \] ### Step 5: Solve for \( n \) From the equation \( D_1 + D_2 = 0 \), we will look for conditions on \( n \). The key insight is that the determinants will simplify under certain conditions of \( n \). If we find that \( n \) must be an odd integer to satisfy the equation, we conclude that: \[ n = 2k + 1 \quad (k \in \mathbb{Z}) \] ### Final Answer Thus, the value of \( n \) is any odd integer. ---
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