CUET Preparation Today
If A is a square matrix of order 2 × 2 and A = 7, then value of |2 Adj. (A)| is: |
21 28 14 7 |
28 |
Given $|A|=7$ For a matrix of order $n$ $|kA|=k^n|A|$ Here $n=2$ $|2A|=2^2|A|$ $|2A|=4\times7=28$ Also $|\text{Adj}(A)|=|A|^{n-1}$ Since $n=2$ $|\text{Adj}(A)|=|A|^{1}=7$ Now $|2\,\text{Adj}(A)|=2^2|\text{Adj}(A)|$ $=4\times7=28$ The value is $28$. |
