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Consider this matrix:

[[3,6],[-10,-10]]
Find the inverse of the matrix. Give exact values. Non-integers can be given as decimals or as simplified fractions.

Consider this matrix:\newline[361010] \left[\begin{array}{cc} 3 & 6 \\ & \\ -10 & -10 \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[361010] \left[\begin{array}{cc} 3 & 6 \\ & \\ -10 & -10 \end{array}\right] \newlineFind the inverse of the matrix. Give exact values. Non-integers can be given as decimals or as simplified fractions.
  1. Write Matrix Determinant: Write down the matrix and its determinant.\newlineThe determinant of a 2×22 \times 2 matrix [ab cd]\left[\begin{array}{cc} a & b \ c & d \end{array}\right] is adbcad - bc.\newlineFor the matrix [36 1010]\left[\begin{array}{cc} 3 & 6 \ -10 & -10 \end{array}\right], the determinant is (3×10)(6×10)(3 \times -10) - (6 \times -10).
  2. Calculate Determinant: Calculate the determinant.\newlineDeterminant = (3×10)(6×10)=30(60)=30+60=30(3 \times -10) - (6 \times -10) = -30 - (-60) = -30 + 60 = 30.
  3. Check Non-Zero Determinant: Check if the determinant is non-zero.\newlineSince the determinant is 3030, which is non-zero, the matrix has an inverse.
  4. Write Inverse Formula: Write down the formula for the inverse of a 2×22 \times 2 matrix.\newlineThe inverse of a 2×22 \times 2 matrix [ab cd]\left[\begin{array}{cc} a & b \ c & d \end{array}\right] is 1determinant×[db ca]\frac{1}{\text{determinant}} \times \left[\begin{array}{cc} d & -b \ -c & a \end{array}\right].
  5. Apply Inverse Formula: Apply the formula to find the inverse of the given matrix.\newlineUsing the formula, the inverse of \left[\begin{array}{cc}3 & 6 \-10 & -10\end{array}\right] is 130\frac{1}{30} * \left[\begin{array}{cc}-10 & -6 \10 & 3\end{array}\right].
  6. Multiply by Scalar: Multiply each element of the matrix by the scalar (1/30)(1/30).\newlineThe inverse matrix is [[10/30,6/30],[10/30,3/30]][[-10/30, -6/30], [10/30, 3/30]].
  7. Simplify Inverse Matrix: Simplify the fractions in the inverse matrix.\newlineThe simplified inverse matrix is [1315 13110]\left[\begin{array}{cc} -\frac{1}{3} & -\frac{1}{5} \ \frac{1}{3} & \frac{1}{10} \end{array}\right].

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