If $A=\left\{x \in C: x^2=1\right\}$ and $B=\left\{x \in C: x^4=1\right\}$, then $A \Delta B$ is equal to
Answer & explanation
Correct answer: option 3
$x^2=1 \Rightarrow x=-1,1$ ∴ $A =\{-1,1\}$
$x^4=1 \Rightarrow x^2=-1,1$
$\Rightarrow x=-i, i,-1,1 . B=\{-i, i,-1,1\} $
∴ $A \Delta B=(A-B) \cup(B-A)=\varphi \cup\{-i, i\}=\{-i, i\}$
Hence (3) is the correct answer.