Mathematics · Matrices

JEE Main 2026 — 6 April, Evening Shift — Question 25

Let A=[[1,0,0],[3,1,0],[9,3,1]]A = [[1,0,0],[3,1,0],[9,3,1]] and B=[bij],1≤i,j≤3.B = [b_ij], 1≤i,j≤3. If B=A99−I,B = A^99 - I, then the value of (b31−b21)b32\frac{(b_{31} - b_{21})}{b_{32}} is:

  1. Option A:

    99

  2. Option B:

    199

  3. Option C:

    149

    Correct
  4. Option D:

    159

Answer: C

Step-by-step solution

A=P+I\mathrm{A}=\mathrm{P}+\mathrm{I} A=[000300930]+[100010001]A=\left[\begin{array}{lll}0 & 0 & 0\\ 3 & 0 & 0\\ 9 & 3 & 0\end{array}\right]+\left[\begin{array}{lll}1 & 0 & 0\\ 0 & 1 & 0\\ 0 & 0 & 1\end{array}\right] A=P+I\mathrm{A}=\mathrm{P}+\mathrm{I} where P3=0\mathrm{P}^{3}=0 A99=I+99P+99C2P2\mathrm{A}^{99}=\mathrm{I}+99 \mathrm{P}+{ }^{99} \mathrm{C}_{2} \mathrm{P}^{2} A99−I=99[000300930]+99C2[000000900]\mathrm{A}^{99}-\mathrm{I}=99\left[\begin{array}{lll}0 & 0 & 0\\ 3 & 0 & 0\\ 9 & 3 & 0\end{array}\right]+{ }^{99} \mathrm{C}_{2}\left[\begin{array}{lll}0 & 0 & 0\\ 0 & 0 & 0\\ 9 & 0 & 0\end{array}\right] =[00099×3004455099×30]=\left[\begin{array}{ccc}0 & 0 & 0\\ 99 \times 3 & 0 & 0\\ 44550 & 99 \times 3 & 0\end{array}\right] b31=44550, b21=99×3, b32=99×3\mathrm{b}_{31}=44550, \mathrm{~b}_{21}=99 \times 3, \mathrm{~b}_{32}=99 \times 3 44550−297297=149\frac{44550-297}{297}=149

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
Matrices
Topic
Inverse of a Matrix