Let the determinant of a square matrix $A$ of order $m$ be $m-n$, where $m$ and $n$ satisfy $4m+n=22$ and…

Let the determinant of a square matrix $A$ of order $m$ be $m-n$, where $m$ and $n$ satisfy $4m+n=22$ and $17m+4n=93$. If $\text{det}(n \, \text{adj}(\text{adj}(mA)))=3^{a}5^{b}6^{c}$, then $a+b+c$ is equal to.
  1. 84
  2. 96
  3. 101
  4. 109

Solution

We have been given that 

A=m-n, where 4m+n=22 .......i

and 17m+4n=93 .......ii

Solving i and ii

m=5, n=2

Order =5

A=3

We know that adjA=Aw-1adjadjA=Aw-12  where w×w is the order of the matrix.

 det n adj adjmA

=2adj adj 5A

=255A16

=25 580 A16=25·316·580

=311 580 65

So, a+b+c=96

Hence this is the required option.

Asked in: JEE Main 2023 (15 Apr Shift 1)

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