Prove that the two matrices

[tex]\[
\left[\begin{array}{cc}-3 & -2 \\ 5 & 3\end{array}\right]
\][/tex]

and

[tex]\[
\left[\begin{array}{cc}3 & 2 \\ -5 & -3\end{array}\right]
\][/tex]

are the inverse of each other.



Answer :

Certainly! To prove that the matrices [tex]\(\left[\begin{array}{cc}-3 & -2 \\ 5 & 3\end{array}\right]\)[/tex] and [tex]\(\left[\begin{array}{cc}3 & 2 \\ -5 & -3\end{array}\right]\)[/tex] are inverses of each other, we need to show that their product equals the identity matrix.

The identity matrix for [tex]\(2 \times 2\)[/tex] matrices is:

[tex]\[ I = \left[\begin{array}{cc}1 & 0 \\ 0 & 1\end{array}\right] \][/tex]

Let's denote the matrices as:
[tex]\[ A = \left[\begin{array}{cc}-3 & -2 \\ 5 & 3\end{array}\right] \][/tex]
[tex]\[ B = \left[\begin{array}{cc}3 & 2 \\ -5 & -3\end{array}\right] \][/tex]

To prove [tex]\(A\)[/tex] and [tex]\(B\)[/tex] are inverses, we must show that [tex]\(AB = I\)[/tex].

Calculating the product [tex]\(AB\)[/tex]:

[tex]\[ AB = \left[\begin{array}{cc}-3 & -2 \\ 5 & 3\end{array}\right] \left[\begin{array}{cc}3 & 2 \\ -5 & -3\end{array}\right] \][/tex]

To find the element in the first row and first column of the product [tex]\(AB\)[/tex]:
[tex]\[ (-3 \times 3) + (-2 \times -5) = -9 + 10 = 1 \][/tex]

To find the element in the first row and second column of the product [tex]\(AB\)[/tex]:
[tex]\[ (-3 \times 2) + (-2 \times -3) = -6 + 6 = 0 \][/tex]

To find the element in the second row and first column of the product [tex]\(AB\)[/tex]:
[tex]\[ (5 \times 3) + (3 \times -5) = 15 - 15 = 0 \][/tex]

To find the element in the second row and second column of the product [tex]\(AB\)[/tex]:
[tex]\[ (5 \times 2) + (3 \times -3) = 10 - 9 = 1 \][/tex]

Putting all these elements together, we get:

[tex]\[ AB = \left[\begin{array}{cc}1 & 0 \\ 0 & 1\end{array}\right] \][/tex]

Since [tex]\(AB = I\)[/tex], we have shown that matrix [tex]\(A\)[/tex] is the inverse of matrix [tex]\(B\)[/tex], and equivalently, matrix [tex]\(B\)[/tex] is the inverse of matrix [tex]\(A\)[/tex]. Thus, we have proven that the matrices [tex]\(\left[\begin{array}{cc}-3 & -2 \\ 5 & 3\end{array}\right]\)[/tex] and [tex]\(\left[\begin{array}{cc}3 & 2 \\ -5 & -3\end{array}\right]\)[/tex] are indeed inverses of each other.