Home
Class 12
MATHS
If A=[(2,3),(1,0)] =P +Q where P is symm...

If `A=[(2,3),(1,0)]` =P +Q where P is symmetric matrix and Q is skew -skew-symmetric matrix then the value of matrix P is :

A

`[(0,-2),(2,0)]`

B

`[(2,2),(2,0)]`

C

`[(2,-2),(-2,0)]`

D

`[(1,2),(0,1)]`

Text Solution

AI Generated Solution

The correct Answer is:
To find the symmetric matrix \( P \) from the equation \( A = P + Q \), where \( A = \begin{pmatrix} 2 & 3 \\ 1 & 0 \end{pmatrix} \), \( P \) is symmetric, and \( Q \) is skew-symmetric, we can follow these steps: ### Step-by-Step Solution 1. **Understand the properties of symmetric and skew-symmetric matrices**: - A matrix \( P \) is symmetric if \( P^T = P \). - A matrix \( Q \) is skew-symmetric if \( Q^T = -Q \). 2. **Write the equation**: \[ A = P + Q \] where \( A = \begin{pmatrix} 2 & 3 \\ 1 & 0 \end{pmatrix} \). 3. **Take the transpose of both sides**: \[ A^T = P^T + Q^T \] Since \( P \) is symmetric, \( P^T = P \), and since \( Q \) is skew-symmetric, \( Q^T = -Q \). Therefore, we can rewrite the equation as: \[ A^T = P - Q \] 4. **Calculate \( A^T \)**: \[ A^T = \begin{pmatrix} 2 & 1 \\ 3 & 0 \end{pmatrix} \] 5. **Now we have two equations**: \[ A = P + Q \quad (1) \] \[ A^T = P - Q \quad (2) \] 6. **Add equations (1) and (2)**: \[ (P + Q) + (P - Q) = A + A^T \] This simplifies to: \[ 2P = A + A^T \] 7. **Calculate \( A + A^T \)**: \[ A + A^T = \begin{pmatrix} 2 & 3 \\ 1 & 0 \end{pmatrix} + \begin{pmatrix} 2 & 1 \\ 3 & 0 \end{pmatrix} = \begin{pmatrix} 4 & 4 \\ 4 & 0 \end{pmatrix} \] 8. **Substitute back to find \( P \)**: \[ 2P = \begin{pmatrix} 4 & 4 \\ 4 & 0 \end{pmatrix} \] Divide both sides by 2: \[ P = \begin{pmatrix} 2 & 2 \\ 2 & 0 \end{pmatrix} \] ### Final Result The value of matrix \( P \) is: \[ P = \begin{pmatrix} 2 & 2 \\ 2 & 0 \end{pmatrix} \]
Promotional Banner