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Consider this matrix:

[[5,-3],[6,-3]]
Find the inverse of the matrix. Give exact values. Non-integers can be given as decimals or as simplified fractions.

Consider this matrix:\newline[5363] \left[\begin{array}{ll} 5 & -3 \\ 6 & -3 \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[5363] \left[\begin{array}{ll} 5 & -3 \\ 6 & -3 \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, we use the formula:\newlineInverse(A)=(1det(A))×adj(A)\text{Inverse}(A) = \left(\frac{1}{\text{det}(A)}\right) \times \text{adj}(A)\newlinewhere det(A)\text{det}(A) is the determinant of matrix AA and adj(A)\text{adj}(A) is the adjugate of matrix AA.\newlineFirst, we need to calculate the determinant of the given matrix.
  2. Find Adjugate: The determinant of a 2×22 \times 2 matrix [ab cd]\left[\begin{array}{cc} a & b \ c & d \end{array}\right] is calculated as adbcad - bc. For our matrix [53 63]\left[\begin{array}{cc} 5 & -3 \ 6 & -3 \end{array}\right], the determinant is (5×3)(6×3)(5 \times -3) - (6 \times -3).
  3. Calculate Inverse: Calculating the determinant:\newlinedet(A)=(5×3)(6×3)(A) = (5 \times -3) - (6 \times -3)\newlinedet(A)=15(18)(A) = -15 - (-18)\newlinedet(A)=15+18(A) = -15 + 18\newlinedet(A)=3(A) = 3\newlineThe determinant of the matrix is 33.
  4. Multiply by 11/33: Next, we need to find the adjugate of the matrix. The adjugate of a 2×22 \times 2 matrix [ab cd]\left[\begin{array}{cc} a & b \ c & d \end{array}\right] is [db ca]\left[\begin{array}{cc} d & -b \ -c & a \end{array}\right]. For our matrix [53 63]\left[\begin{array}{cc} 5 & -3 \ 6 & -3 \end{array}\right], the adjugate is [33 65]\left[\begin{array}{cc} -3 & 3 \ -6 & 5 \end{array}\right].
  5. Simplify Fraction: Now we can find the inverse of the matrix by multiplying the adjugate by 1det(A)\frac{1}{\det(A)}.\newlineInverse(A)=13×[33 65](A) = \frac{1}{3} \times \begin{bmatrix} -3 & 3 \ -6 & 5 \end{bmatrix}
  6. Simplify Fraction: Now we can find the inverse of the matrix by multiplying the adjugate by 1/det(A)1/\text{det}(A). \newlineInverse(A)=(1/3)×[33 65](A) = (1/3) \times \left[\begin{array}{cc} -3 & 3 \ -6 & 5 \end{array}\right] Multiplying the adjugate by 1/31/3: \newlineInverse(A)=[(3/3)(3/3) (6/3)(5/3)](A) = \left[\begin{array}{cc} (-3/3) & (3/3) \ (-6/3) & (5/3) \end{array}\right] \newlineInverse(A)=[11 25/3](A) = \left[\begin{array}{cc} -1 & 1 \ -2 & 5/3 \end{array}\right]
  7. Simplify Fraction: Now we can find the inverse of the matrix by multiplying the adjugate by 1/det(A)1/\text{det}(A). \newlineInverse(A)=(1/3)×[33 65](A) = (1/3) \times \left[\begin{array}{cc} -3 & 3 \ -6 & 5 \end{array}\right] Multiplying the adjugate by 1/31/3: \newlineInverse(A)=[(3/3)(3/3) (6/3)(5/3)](A) = \left[\begin{array}{cc} (-3/3) & (3/3) \ (-6/3) & (5/3) \end{array}\right] \newlineInverse(A)=[11 25/3](A) = \left[\begin{array}{cc} -1 & 1 \ -2 & 5/3 \end{array}\right] We can simplify the fraction 5/35/3 to its decimal equivalent if needed. \newline5/35/3 is approximately 1.66671.6667. \newlineSo the inverse matrix can also be written as: \newlineInverse(A)=[11 21.6667](A) = \left[\begin{array}{cc} -1 & 1 \ -2 & 1.6667 \end{array}\right]

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