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JEE Main202118 Mar 2021Evening ShiftMathematicsSets and RelationsActual

Define a relation R over a class of n × n real matrices A and B as " A R B iff there exists a non-singular matrix P such that P A P - 1 = B ". Then which of the following is true ?

Options

  1. AR is symmetric, transitive but not reflexive
  2. BR is reflexive, symmetric but not transitive
  3. CR is an equivalence relation
  4. DR is reflexive, transitive but not symmetric

Correct answer

C. R is an equivalence relation

Step-by-step solution

Given A and B are matrices of n × n order and A R B iff there exists a non-singular matrix P   det P ≠ 0 such that P A P - 1 = B . Reflexivity Check : A R A ⇒ P A P - 1 = A which is true for P = I . So, R is reflexive relation. Symmetric Check : A R B ⇒ P A P - 1 = B ⇒ P - 1 P A P - 1 P = P - 1 B P ⇒ I A I = P - 1 B P ⇒ P - 1 B P = A ⇒ B R A for matrix P - 1 . So, R is symmetric relation. Transitivity Check : A R B ⇒ P A P - 1 = B and B R C ⇒ P B P - 1

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