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← JEE Advanced 2022 · Paper 2
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JEE Advanced 2022 · Paper 2, Mathematics question 16

If M=(5232−32−12)M = \begin{pmatrix}\frac52 & \frac32\\ -\frac32 & -\frac12\end{pmatrix}, then which of the following matrices is equal to M2022M^{2022}?

Choose one option
Answer and worked solution

Official answer: A

Split off the identity.
M=I+N,N=(3232−32−32),N2=0.M=I+N,\qquad N=\begin{pmatrix}\frac32&\frac32\\-\frac32&-\frac32\end{pmatrix},\qquad N^2=0.

Powers. Since N2=0N^2=0, Mn=I+nNM^n=I+nN. With n=2022n=2022, 3n2=3033\frac{3n}2=3033:
M2022=(1+30333033−30331−3033)=(30343033−3033−3032).M^{2022}=\begin{pmatrix}1+3033&3033\\-3033&1-3033\end{pmatrix}=\begin{pmatrix}3034&3033\\-3033&-3032\end{pmatrix}.
(A).