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Find the inverse of the matrix below.

[tex]\[
\begin{pmatrix}
9 & 2 \\
16 & 4
\end{pmatrix}
\][/tex]

If necessary, round to the nearest hundredth.


Sagot :

To find the inverse of the given matrix, we start with the matrix:
[tex]\[ \begin{bmatrix} 9 & 2 \\ 16 & 4 \end{bmatrix} \][/tex]

The formula to find the inverse of a 2x2 matrix
[tex]\[ \begin{bmatrix} a & b \\ c & d \end{bmatrix} \][/tex]
is given by:
[tex]\[ \frac{1}{ad - bc} \begin{bmatrix} d & -b \\ -c & a \end{bmatrix} \][/tex]

Let's apply this formula to our matrix.

First, identify the elements of the matrix:
[tex]\[ a = 9, \quad b = 2, \quad c = 16, \quad d = 4 \][/tex]

Next, we need to calculate the determinant [tex]\( ad - bc \)[/tex]:
[tex]\[ \text{Determinant} = ad - bc = (9 \times 4) - (2 \times 16) = 36 - 32 = 4 \][/tex]

Since the determinant is non-zero (in this case, 4), the matrix has an inverse.

The inverse matrix [tex]\( \frac{1}{ad - bc} \begin{bmatrix} d & -b \\ -c & a \end{bmatrix} \)[/tex] in our case is:
[tex]\[ \frac{1}{4} \begin{bmatrix} 4 & -2 \\ -16 & 9 \end{bmatrix} \][/tex]

Now, multiply each element of the matrix by [tex]\( \frac{1}{4} \)[/tex]:
[tex]\[ \begin{bmatrix} 4 \times \frac{1}{4} & -2 \times \frac{1}{4} \\ -16 \times \frac{1}{4} & 9 \times \frac{1}{4} \end{bmatrix} = \begin{bmatrix} 1 & -0.5 \\ -4 & 2.25 \end{bmatrix} \][/tex]

So, the inverse of the matrix
[tex]\[ \begin{bmatrix} 9 & 2 \\ 16 & 4 \end{bmatrix} \][/tex]
is
[tex]\[ \begin{bmatrix} 1 & -0.5 \\ -4 & 2.25 \end{bmatrix} \][/tex]

All the elements are already rounded as needed. Therefore, the inverse matrix rounded to the nearest hundredth is:
[tex]\[ \begin{bmatrix} 1 & -0.5 \\ -4 & 2.25 \end{bmatrix} \][/tex]