To find the inverse of matrix \( P \), we will use the formula for the inverse of a 2×2 matrix:
\[
P^{-1} = \frac{1}{\text{det}(P)} \begin{pmatrix} d & -b \\ -c & a \end{pmatrix}
\]
where the matrix \( P = \begin{pmatrix} a & b \\ c & d \end{pmatrix} \).
Step 1: Identify the elements of \( P \)
From the matrix \( P = \begin{pmatrix} 2 & 1 \\ -3 & 1 \end{pmatrix} \), we have:
– \( a = 2 \)
– \( b = 1 \)
– \( c = -3 \)
– \( d = 1 \)
Step 2: Calculate the determinant of \( P \)
The determinant of \( P \) is given by:
\[
\text{det}(P) = ad – bc = 2(1) – 1(-3) = 2 + 3 = 5
\]
Step 3: Apply the formula for the inverse
Substitute the values into the formula for \( P^{-1} \):
\[
P^{-1} = \frac{1}{5} \begin{pmatrix} 1 & -1 \\ 3 & 2 \end{pmatrix}
\]
Thus, the inverse of \( P \) is:
\[
P^{-1} = \begin{pmatrix} \frac{1}{5} & -\frac{1}{5} \\ \frac{3}{5} & \frac{2}{5} \end{pmatrix}
\]
Step 4: Final Answer
So, the inverse of \( P \) is:
\[
\boxed{\begin{pmatrix} \frac{1}{5} & -\frac{1}{5} \\ \frac{3}{5} & \frac{2}{5} \end{pmatrix}}
\]
Option List:
- \( \begin{pmatrix} -\frac{1}{5} & -\frac{1}{5} \\ -\frac{3}{5} & -\frac{2}{5} \end{pmatrix} \)
- \( \begin{pmatrix} \frac{1}{5} & \frac{1}{5} \\ \frac{3}{5} & \frac{2}{5} \end{pmatrix} \)
- \( \begin{pmatrix} -\frac{1}{5} & -\frac{1}{5} \\ \frac{3}{5} & \frac{2}{5} \end{pmatrix} \)
- \( \begin{pmatrix} \frac{1}{5} & -\frac{1}{5} \\ \frac{3}{5} & \frac{2}{5} \end{pmatrix} \)
Thus, the correct answer is D.