MCQ
જો $A$ અને $B$ બે શ્રેણિક હોય જેના માટે $AB=B$ અને $BA=A$ તો ${{A}^{2}}+{{B}^{2}}=........$
  • A
    $2AB$
  • B
    $2BA$
  • C
    $AB$
  • $A+B$

Answer

Correct option: D.
$A+B$
D

$A^2 + B^2 = (BA)^2 + (AB)^2$

$= (BA) (BA) + (AB) (AB)$

$= B (AB) A + A (BA) B$

$= B (BA) + A (AB)$

$= BA + AB$

$A^2 + B^2 = A + B$

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