If A = [(2,1),(3,4)], then (adj A)A = ... (a) [(1/5,0),(0,1/5)] (b) [(1,0),(0,1)] (c) [(5,0),(0,-5)] (d) [(5,0),(0,5)]

Question

If A = \(\begin{bmatrix} 2 &1 \\[0.3em] 3&4\\[0.3em] \end{bmatrix}\), then (adj A)A = ...

(a) \(\begin{bmatrix} 1/5 &0\\[0.3em] 0&1/5\\[0.3em] \end{bmatrix}\)

(b) \(\begin{bmatrix} 1 &0\\[0.3em] 0&1\\[0.3em] \end{bmatrix}\)

(c) \(\begin{bmatrix} 5 &0\\[0.3em] 0&-5\\[0.3em] \end{bmatrix}\)

(d) \(\begin{bmatrix} 5 &0\\[0.3em] 0&5\\[0.3em] \end{bmatrix}\)

Answer 1

(d) \(\begin{bmatrix} 5 &0\\[0.3em] 0&5\\[0.3em] \end{bmatrix}\)

(adj A)(A) = |A|I