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4-1.Complex numbers
medium
If $z=x+i y, x y \neq 0$, satisfies the equation $z^2+i \bar{z}=0$, then $\left|z^2\right|$ is equal to:
A
$9$
B
$1$
C
$4$
D
$\frac{1}{4}$
(JEE MAIN-2024)
Solution
$ z^2=-i \bar{z} $
$ \left|z^2\right|=|i \bar{z}|$
$ \left|z^2\right|=|z|$
$ |z|^2-|z|=0$
$ |z|(|z|-1)=0$
$ |z|=0 \text { (not acceptable) } $
$ \therefore|z|=1 $
$ \therefore|z|^2=1$
Standard 11
Mathematics