JEE Main20202 Sep 2020Morning ShiftMathematicsMatricesActual
Let A be a 2 × 2 real matrix with entries from 0 , 1 and A ≠ 0 . Consider the following two statements; P If A ≠ l 2 , then A = - 1 Q If A = 1 , then t r A = 2 Where l 2 denotes 2 × 2 identity matrix and t r A denotes the sum of the diagonal entries of A . Then
Options
- AP is false and Q is true
- BBoth P and Q are false
- CP is true and Q is false
- DBoth P and Q are true
Correct answer
D. Both P and Q are true
Step-by-step solution
Let A = a b c d    a , b , c , d ∈ 0 , 1 A = a d - b c ≠ 0 ⇒   a d = 1 , b c = 0 or a d = 0 , b c = 1 P If A ≠ I 2 ⇒ a d ≠ 1 ⇒ a d = 0 , b c = 1 ⇒ | A | = - 1 P is true. Q If A = 1 ⇒ a d = 1 , b c = 0 ⇒   tr ( A ) = 2 Q is true.