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Let A=[a0b0]A=\begin{bmatrix}a & 0 \\ b & 0\end{bmatrix} and A2=[4c20]A^2=\begin{bmatrix}4 & c \\ 2 & 0\end{bmatrix}, a,b,c∈Za,b,c \in \mathbb{Z}. Then the minimum value of a+b+ca+b+c is:

Solution

✅ Correct Option: 3

A2=[a20ab0]A^2 = \begin{bmatrix}a^2 & 0\\ab & 0\end{bmatrix}, so a2=4a^2 = 4, ab=2ab = 2 and c=0c = 0.

This gives (a,b)=(2,1)(a,b) = (2,1) or (−2,−1)(-2,-1).

Hence a+b+ca+b+c is 33 or −3-3, and the minimum is −3-3.

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