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A matrix has eigenvalues -1 and -2. The corresponding eigenvectors are \(\left[ \begin{matrix} 1 \\\ -1 \end{matrix} \right]\) and \(\left[ \begin{matrix} 1 \\\ -2 \end{matrix} \right]\) respectively. The matrix is
1. \(\left[ \begin{matrix} 1 && 1 \\\ -1 && -2 \end{matrix} \right]\)
2. \(\left[ \begin{matrix} 1 && 2 \\\ -2 && -4 \end{matrix} \right]\)
3. \(\left[ \begin{matrix} -1 && 0 \\\ 0 && -2 \end{matrix} \right]\)
4. \(\left[ \begin{matrix} 0 && 1 \\\ -2 && -3 \end{matrix} \right]\)
5.

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Correct Answer - Option 4 : \(\left[ \begin{matrix} 0 && 1 \\\ -2 && -3 \end{matrix} \right]\)

For a matrix A, whose eigen value is \(λ\) and corresponding eigen vector is X, C.E. equation is given by

AX=λ X

Assume, \(A= \begin{pmatrix} a & b\\ c & d \end{pmatrix}\)

For eigen value λ = -1⇒

\(\begin{pmatrix} a & b\\ c & d \end{pmatrix}\begin{pmatrix} +1 \\ -1 \end{pmatrix}=(-1)\begin{pmatrix} +1 \\ -1 \end{pmatrix} \)

\(a-b=-1\space\space\space\space\space\space \space...(i)\)

\(c-d=-1\space\space\space\space\space\space \space...(ii)\)

For eigen value λ = -2⇒

\(\begin{pmatrix} a & b\\ c & d \end{pmatrix}\begin{pmatrix} +1 \\ -2 \end{pmatrix}=(-2)\begin{pmatrix} +1 \\ -2 \end{pmatrix} \)

\(a-2b=-2\space\space\space\space\space\space \space...(ii)\)

\(c-2d=4\space\space\space\space\space\space \space...(iv) \)

From (i) - (iii)

b= -1+2 = 1

from (i)

a = 0

From (ii) - (iv)

d = -3

From (ii)

c = -2

So matrix \(A= \begin{pmatrix} 0 & 1\\ -2 & -3 \end{pmatrix} \)

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