$\left| {\frac{1}{2}({z_1} + {z_2}) + \sqrt {{z_1}{z_2}} } \right| + \left| {\frac{1}{2}({z_1} + {z_2}) - \sqrt {{z_1}{z_2}} } \right|$ =
$|{z_1} + {z_2}|$
$|{z_1} - {z_2}|$
$|{z_1}| + |{z_2}|$
$|{z_1}| - |{z_2}|$
Let $z$ be a complex number, then the equation ${z^4} + z + 2 = 0$ cannot have a root, such that
Let $z$ and $w$ be the two non-zero complex numbers such that $|z|\, = \,|w|$ and $arg\,z + arg\,w = \pi $. Then $z$ is equal to
Let ${z_1}$ be a complex number with $|{z_1}| = 1$ and ${z_2}$be any complex number, then $\left| {\frac{{{z_1} - {z_2}}}{{1 - {z_1}{{\bar z}_2}}}} \right| = $
Find the modulus of $\frac{1+i}{1-i}-\frac{1-i}{1+i}$
If ${z_1} = 1 + 2i$ and ${z_2} = 3 + 5i$, and then $\operatorname{Re} \left( {\frac{{{{\bar z}_2}{z_1}}}{{{z_2}}}} \right)$ is equal to