Use the fact that if , then to find the inverse of each matrix, if possible. Check that and . A=[3−4−12]
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Identify the elements of matrix \(A\): \(a = 3\), \(b = -1\), \(c = -4\), and \(d = 2\).
Calculate the determinant of \(A\) using the formula \(ad - bc\): compute \(3 \times 2 - (-1) \times (-4)\).
Check if the determinant is non-zero. If it is zero, the inverse does not exist; if non-zero, proceed to find the inverse.
Use the inverse formula \(A^{-1} = \frac{1}{ad - bc} \begin{bmatrix} d & -b \\ -c & a \end{bmatrix}\) and substitute the values of \(a\), \(b\), \(c\), and \(d\).
Multiply the scalar \(\frac{1}{ad - bc}\) by the matrix \(\begin{bmatrix} d & -b \\ -c & a \end{bmatrix}\) to write the inverse matrix explicitly.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Matrix Inverse
The inverse of a square matrix A, denoted A⁻¹, is a matrix that when multiplied by A yields the identity matrix I. For a 2x2 matrix, the inverse exists only if the determinant (ad - bc) is nonzero. The formula for the inverse involves swapping elements a and d, changing signs of b and c, and dividing by the determinant.
The determinant of a 2x2 matrix A = [[a, b], [c, d]] is calculated as ad - bc. It is a scalar value that indicates whether the matrix is invertible; if the determinant is zero, the matrix has no inverse. The determinant also provides information about the matrix's scaling factor and orientation.
The identity matrix I₂ is a 2x2 matrix with ones on the diagonal and zeros elsewhere. Multiplying any 2x2 matrix A by I₂ leaves A unchanged. To verify an inverse, multiply A by A⁻¹ and A⁻¹ by A; both products should equal I₂, confirming the correctness of the inverse.