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QJEEM24Ma005f: JEE Main 2024 Mathematics - Class 12 JEEM24Ma005f Solution: Let , where is a real matrix of order such that the relation…

Let A=I2−2MMTA=I_2-2 M M^T , where MM is a real matrix of order 2×12 \times 1 such that the relation MTM=I1M^T M=I_1 holds. If λ\lambda is a real number such that the relation AX=λXA X=\lambda X holds for some non-zero real matrix XX of order 2×12 \times 1 , then the sum of squares of all possible values of λ\lambda is equal to __________.

Step-by-Step Verified Solution

amp;A=I2−2MTamp;A2=(I2−2MMT)(I2−2MT)amp;=I2−2MT−2MMT+4MTMTamp;=I2−4MMT+4MMTamp;=I2\begin{aligned} & A=I_2-2 M^T \\\\ & A^2=\left(I_2-2 M M^T\right)\left(I_2-2 M^T\right) \\\\ & =I_2-2 M^T-2 M M^T+4 M^T M^T \\\\ & =I_2-4 M M^T+4 M M^T \\\\ & =I_2\end{aligned}

amp;AX=λXamp;A2X=λAXamp;X=λ(λX)amp;X=λ2Xamp;X(λ2−1)=0amp;λ2=1amp;λ=±1\begin{aligned} & \mathrm{AX}=\lambda \mathrm{X} \\\\ & \mathrm{A}^2 \mathrm{X}=\lambda \mathrm{AX} \\\\ & \mathrm{X}=\lambda(\lambda \mathrm{X}) \\\\ & \mathrm{X}=\lambda^2 \mathrm{X} \\\\ & \mathrm{X}\left(\lambda^2-1\right)=0 \\\\ & \lambda^2=1 \\\\ & \lambda= \pm 1\end{aligned}

Sum of square of all possible values =2=2

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