If A is a   3 × 3 matrix such that 5   a d j A = 5 , then A is equal to

If A is a  3×3 matrix such that 5 adjA=5, then A is equal to
  1. ±125
  2. ±5
  3. ±15
  4. ±1

Solution

5 Adj A=5

125 |adj A|=5

Since [A] is 3×3

adj A=125

A2=125

A= ±15.

Asked in: JEE Main 2015 (11 Apr Online)

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