Question

If A=[1 2 3
1 3 5
1 5 12]
compute adjoint A and
verity that A (adj A) = |A|.I.
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Answer 1

(i) = (cos θ)(cos θ) − (−sin θ)(sin θ) = cos2 θ+ sin2 θ = 1

(ii)

= (x2 − x + 1)(x + 1) − (x − 1)(x + 1)

= x3 − x2 + x + x2 − x + 1 − (x2 − 1)

= x3 + 1 − x2 + 1

= x3 − x2 + 2