Q35 / 124 · NTA Abhyas (JEE Main) 2020 · Mathematics · Determinants

Let matrix A=xy-z12  311  2, where x, y, z∈N. If adjadjadjadjA=48·516, then the number of such matrices A is equal to (where, M represents determinant of a matrix M)

Correct answer: 36

Solution

det.adjadjadjadjA=A3-14
=A16=48.516
⇒A=±10
A=xy-z123112=x+y+z=±10
∵x,y,z∈N⇒x+y+z=-10 (not possible)
Hence, x+y+z=10
The number of such matrices =9C2
=36

Hence, the correct answer is 36.

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