 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2011/paper-1/13/a/ii/solution

Interchange the diagonal entries, negate the off-diagonal entries, and divide by the nonzero determinant. The matrix inverse is

A^{- 1} = \frac{1}{16} (5335) .

A

gives the identity matrix, since each diagonal product sum is

25 - 9 = 16

and each off-diagonal product sum is zero.

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