The inverse matrix of [tex]\(\left[\begin{array}{ll}2 & 3 \\ 5 & 9\end{array}\right]\)[/tex] is [tex]\(\frac{1}{k}\left[\begin{array}{cc}9 & -3 \\ m & 2\end{array}\right]\)[/tex].

Find the values of [tex]\(k\)[/tex] and [tex]\(m\)[/tex].



Answer :

To find the values of [tex]\( k \)[/tex] and [tex]\( m \)[/tex] for the inverse matrix of [tex]\(\left[\begin{array}{cc}2 & 3 \\ 5 & 9\end{array}\right]\)[/tex] given as [tex]\(\frac{1}{k}\left[\begin{array}{cc}9 & -3 \\ m & 2\end{array}\right]\)[/tex], we proceed with the following steps:

1. Finding the Determinant of the Matrix:

Let [tex]\( A = \left[\begin{array}{cc}2 & 3 \\ 5 & 9\end{array}\right] \)[/tex].

The determinant of matrix [tex]\( A \)[/tex], denoted as [tex]\( \det(A) \)[/tex], is calculated as:

[tex]\[ \det(A) = (2 \cdot 9) - (3 \cdot 5) = 18 - 15 = 3 \][/tex]

Therefore, [tex]\( k = 3 \)[/tex].

2. Finding the Inverse of the Matrix:

The formula for the inverse of a [tex]\( 2 \times 2 \)[/tex] matrix [tex]\( \left[\begin{array}{cc}a & b \\ c & d\end{array}\right] \)[/tex] is:

[tex]\[ A^{-1} = \frac{1}{\det(A)} \left[\begin{array}{cc}d & -b \\ -c & a\end{array}\right] \][/tex]

Using the elements of our matrix [tex]\( A \)[/tex]:

[tex]\[ A^{-1} = \frac{1}{3} \left[\begin{array}{cc}9 & -3 \\ -5 & 2\end{array}\right] \][/tex]

3. Comparing the Inverse Matrix:

We are given the form of the inverse matrix as [tex]\(\frac{1}{k}\left[\begin{array}{cc}9 & -3 \\ m & 2\end{array}\right]\)[/tex].

From the calculated inverse, we have:

[tex]\[ A^{-1} = \frac{1}{3} \left[\begin{array}{cc}9 & -3 \\ -5 & 2\end{array}\right] = \left[\begin{array}{cc}\frac{9}{3} & \frac{-3}{3} \\ \frac{-5}{3} & \frac{2}{3}\end{array}\right] \][/tex]

By comparison, we see:

[tex]\[ k = 3 \quad \text{and} \quad m = -5 \][/tex]

Thus, the values are:

[tex]\[ k = 3 \quad \text{and} \quad m = -5 \][/tex]

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