Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Matrices

Question:

If A and B are square matrices such that $A^* = A$ and $B^* = B$, where $A^*$ denotes the conjugate transpose of A, then $(AB-BA)^* =$

Options:

Null matrix

$AB-BA$

$BA - AB$

none of these

Correct Answer:

$BA - AB$

Explanation:

We have,

$(AB-BA)^* = (\overline{AB-BA})^T= (\overline{A}\, \overline{B}- \overline{B}\,\overline{A})^T=(\overline{A}\, \overline{B})^T - (\overline{B}\,\overline{A})^T$

$⇒(AB-BA)^* = (\overline{B})^T (\overline{A})^T (\overline{A})^T (\overline{B})^T - = -B^* A^* A^* B^*$

$⇒(AB-BA)^* = BA-AB$