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Consider this matrix:

[[-4,0],[-10,-6]]
Find the inverse of the matrix. Give exact values. Non-integers can be given as decimals or as simplified fractions.

Consider this matrix:\newline[40106] \left[\begin{array}{cc} -4 & 0 \\ & \\ -10 & -6 \end{array}\right] \newlineFind the inverse of the matrix. Give exact values. Non-integers can be given as decimals or as simplified fractions.

Full solution

Q. Consider this matrix:\newline[40106] \left[\begin{array}{cc} -4 & 0 \\ & \\ -10 & -6 \end{array}\right] \newlineFind the inverse of the matrix. Give exact values. Non-integers can be given as decimals or as simplified fractions.
  1. Calculate determinant: To find the inverse of a 2×22 \times 2 matrix given by [ab cd]\left[\begin{array}{cc} a & b \ c & d \end{array}\right], we use the formula for the inverse of a 2×22 \times 2 matrix: 1adbc×[db ca]\frac{1}{ad - bc} \times \left[\begin{array}{cc} d & -b \ -c & a \end{array}\right]. First, we need to calculate the determinant adbcad - bc.
  2. Determinant calculation: The determinant of our matrix [[4,0],[10,6]][[-4,0],[-10,-6]] is calculated as (4)(6)(0)(10)(-4)\cdot(-6) - (0)\cdot(-10).
  3. Find inverse matrix: The determinant is (4)(6)(0)(10)=240=24(-4)\cdot(-6) - (0)\cdot(-10) = 24 - 0 = 24.
  4. Multiply by reciprocal: Now that we have the determinant, we can find the inverse by multiplying the reciprocal of the determinant by the matrix [[d,b],[c,a]][[d, -b], [-c, a]]. For our matrix, a=4a = -4, b=0b = 0, c=10c = -10, and d=6d = -6. So the matrix [[d,b],[c,a]][[d, -b], [-c, a]] becomes [[6,0],[10,4]][[-6, 0], [10, -4]].
  5. Calculate inverse matrix: Multiplying the reciprocal of the determinant, which is 124\frac{1}{24}, by the matrix [60 104]\left[\begin{array}{cc} -6 & 0 \ 10 & -4 \end{array}\right] gives us the inverse matrix. We perform the multiplication for each element of the matrix.
  6. Simplify fractions: The inverse matrix is 124×[60 104]\frac{1}{24} \times \left[\begin{array}{cc} -6 & 0 \ 10 & -4 \end{array}\right] which simplifies to [624024 1024424]\left[\begin{array}{cc} \frac{-6}{24} & \frac{0}{24} \ \frac{10}{24} & \frac{-4}{24} \end{array}\right].
  7. Final inverse matrix: Simplify the fractions in the matrix to get [140 51216]\left[\begin{array}{cc} -\frac{1}{4} & 0 \ \frac{5}{12} & -\frac{1}{6} \end{array}\right]. This is the inverse of the original matrix.

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