For real numbers $a$ and $b$,if $4a + i(3a - b) = b - 6i$ and $z = a + \frac{b}{4}i$,then $\frac{|z|}{a} = $

If $m_1, m_2, m_3$ and $m_4$ respectively denote the moduli of the complex numbers $1+4 i, 3+i, 1-i$ and $2-3 i$,then the correct one,among the following is

If ${z_1}$ and ${z_2}$ are two complex numbers,then $|{z_1} - {z_2}|$ is

If $z_1, z_2$ are two complex numbers satisfying $\left|\frac{z_1-3 z_2}{3-z_1 \bar{z}_2}\right|=1$ and $\left|z_1\right| \neq 3$,then $\left|z_2\right|$ is equal to

If ${z_1}$ and ${z_2}$ are any two complex numbers,then $|{z_1} + {z_2}|^2 + |{z_1} - {z_2}|^2$ is equal to:

If $\alpha$ and $\beta$ are different complex numbers with $|\beta| = 1$,then $\left| \frac{\beta - \alpha}{1 - \overline{\alpha}\beta} \right|$ is equal to