Allied & ICAR Exam Bank • ALLIED_0002 MCQ • 2 Marks

Section 1: Engineering Mathematics

Linear Algebra

Subtopic: Cayley–Hamilton theorem

Question Statement:

A $2 \times 2$ matrix $A$ has the characteristic equation $\lambda^2 - 5\lambda + 6 = 0$. By the Cayley–Hamilton theorem, the inverse matrix $A^{-1}$ can be expressed as:

Options:

  • (A) $\frac{1}{6}(5I - A)$
  • (B) $\frac{1}{6}(A - 5I)$
  • (C) $5A - 6I$
  • (D) $\frac{1}{5}(6I - A)$

Answer Key:

A

Step-by-Step Solution & Explanation

By Cayley-Hamilton theorem, $A^2 - 5A + 6I = 0 \implies 6A^{-1} = 5I - A \implies A^{-1} = \frac{1}{6}(5I - A)$.
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