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Home  >>  CBSE XII  >>  Math  >>  Relations and Functions
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The identity element for the binary operation $\ast$ defined on $Q\sim \{0\}$ as $a\ast b=\large{\frac{ab}{2}} \normalsize \;a,b\in Q\sim\{0\}$ is

(A) 1 (B) 0 (C) 2 (D) none of these
Can you answer this question?
 
 

1 Answer

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Toolbox:
  • 'e' is the identity element for binary operation * on Q-{0} if
  • $ a *e=e *a=a$
$ a* b=\frac{ab}{2} \qquad a,b \in Q-\{0\}$
 
$ a* b=a => \frac{ab}{2}=a$
 
$=> b=2$
 
$a*2=\frac{a.2}{2}=a$
 
$2*a=\frac{2.a}{2}=a$
 
e=2 is the identity element for * operation
 
'c' option is correct
answered Mar 5, 2013 by meena.p
edited Apr 1 by pady_1
 

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