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If A=|{:(2,lambda,-3),(0,2,5),(1,1,3):}|...

If `A=|{:(2,lambda,-3),(0,2,5),(1,1,3):}|`. Then `A^(-1)` exist if

A

`lambda=2`

B

`lambda ne 2`

C

`lambda ne -2`

D

None of these

Text Solution

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The correct Answer is:
To determine the conditions under which the inverse of the matrix \( A \) exists, we need to calculate the determinant of the matrix \( A \) and find the values of \( \lambda \) for which this determinant is not equal to zero. Given the matrix: \[ A = \begin{pmatrix} 2 & \lambda & -3 \\ 0 & 2 & 5 \\ 1 & 1 & 3 \end{pmatrix} \] ### Step 1: Calculate the Determinant of Matrix \( A \) The determinant of a \( 3 \times 3 \) matrix can be calculated using the formula: \[ \text{det}(A) = a(ei - fh) - b(di - fg) + c(dh - eg) \] where the matrix is represented as: \[ \begin{pmatrix} a & b & c \\ d & e & f \\ g & h & i \end{pmatrix} \] For our matrix \( A \): - \( a = 2 \), \( b = \lambda \), \( c = -3 \) - \( d = 0 \), \( e = 2 \), \( f = 5 \) - \( g = 1 \), \( h = 1 \), \( i = 3 \) Using the determinant formula: \[ \text{det}(A) = 2 \cdot (2 \cdot 3 - 5 \cdot 1) - \lambda \cdot (0 \cdot 3 - 5 \cdot 1) + (-3) \cdot (0 \cdot 1 - 2 \cdot 1) \] ### Step 2: Simplify the Determinant Expression Calculating each term: - First term: \( 2 \cdot (6 - 5) = 2 \cdot 1 = 2 \) - Second term: \( -\lambda \cdot (0 - 5) = 5\lambda \) - Third term: \( -3 \cdot (0 - 2) = 6 \) Putting it all together: \[ \text{det}(A) = 2 + 5\lambda + 6 \] \[ \text{det}(A) = 5\lambda + 8 \] ### Step 3: Set the Determinant Not Equal to Zero For the inverse of \( A \) to exist, we need: \[ \text{det}(A) \neq 0 \] This gives us the condition: \[ 5\lambda + 8 \neq 0 \] ### Step 4: Solve for \( \lambda \) Solving the inequality: \[ 5\lambda \neq -8 \] \[ \lambda \neq -\frac{8}{5} \] ### Conclusion The inverse of the matrix \( A \) exists if: \[ \lambda \neq -\frac{8}{5} \]
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