JEE Advance - Mathematics (2025 - Paper 2 Online - No. 5)
Explanation
Let us consider the matrices given:
$ I = \begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix} $
$ P = \begin{pmatrix} 2 & 0 \\ 0 & 3 \end{pmatrix} $
$ Q = \begin{pmatrix} x & y \\ z & 4 \end{pmatrix} $
$ R = \begin{pmatrix} a & b \\ c & d \end{pmatrix} $
where $ x, y, z, a, b, c, d $ are non-zero real numbers. We aim to verify properties of matrix $ Q $ given the relation $ Q R = R P $.
Steps and Calculations
Matrix Equation Analysis:
Given $ Q R = R P $, we equate both sides:
$ \begin{pmatrix} a x + c y & b x + d y \\ a z + 4c & b z + 4d \end{pmatrix} = \begin{pmatrix} 2a & 3b \\ 2c & 3d \end{pmatrix} $
From the matrix equality, we derive the following key equations:
$ a x + c y = 2a $
$ b x + d y = 3b $
$ a z + 4c = 2c $
$ b z + 4d = 3d $
Determinant Condition:
Comparing the equations:
Set $ a z = -2c $ and $ b z = -d $, resulting in $ \frac{a}{b} = \frac{2c}{d} $.
The requirement $ |R| \neq 0 $ implies $ |P| = |Q| $. So, equating determinants gives us:
$ |P| = |Q| \Rightarrow 6 = 4x - yz \quad \text{(Equation 1)} $
Condition for Non-Trivial Solutions:
From:
$ a(x - z) + c y = 0 $
$ a z + 2c = 0 $
implies a non-trivial solution matrix must have:
$ \left|\begin{array}{cc} x-2 & y \\ z & 2 \end{array}\right| = 0 \Rightarrow 2x - yz = 4 \quad \text{(Equation 2)} $
Solve for $ x $, $ yz $:
Solving Equations 1 and 2:
$ 4x - yz = 6 $
$ 2x - yz = 4 $
Subtract the second from the first:
$ (4x - yz) - (2x - yz) = 6 - 4 \Rightarrow 2x = 2 \Rightarrow x = 1 $
Plugging $ x = 1 $ back, we find:
$ 4(1) - yz = 6 \Rightarrow 4 - yz = 6 \Rightarrow yz = -2 $
Verify Determinants:
For $ Q - 2I $:
$ |Q - 2I| = \left|\begin{array}{cc} x-2 & y \\ z & 2 \end{array}\right| = 2x - yz = 0 $
For $ Q - 6I $:
$ |Q - 6I| = \left|\begin{array}{cc} x-6 & y \\ z & -2 \end{array}\right| = -2x + 12 - yz = 12 $
For $ Q - 3I $:
$ |Q - 3I| = \left|\begin{array}{cc} x-3 & y \\ z & 1 \end{array}\right| = x - 3 - yz = 0 $
Therefore, using the derived values, the statements for the determinants align correctly. The findings are:
$ |Q - 2I| = 0 $
$ |Q - 6I| = 12 $
$ yz = -2 $
These calculations validate the conditions for matrix $ Q $ concerning the predefined matrix properties.
Comments (0)
