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The eigenvalues of the matrix with rows (4, 1) and (2, 3) are

  • A.5 and 2
  • B.4 and 3
  • C.7 and 10
  • D.1 and 6

Answer: A

The trace is \( 4+3=7 \) and the determinant \( (4)(3)-(1)(2)=10 \), so:

\[ \lambda^{2} - (\operatorname{tr}A)\lambda + \det A = 0 \quad\Rightarrow\quad \lambda^{2} - 7\lambda + 10 = 0 \]

\[ (\lambda-5)(\lambda-2)=0 \quad\Rightarrow\quad \lambda = 5,\; 2 \]

They duly sum to 7 and multiply to 10, which is the check.

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