How do I get the square root of a complex number? If I'm given a complex number (say $9 + 4i$), how do I calculate its square root?

$x^2 - y^2 +2ixy$ = write the complex no.
$x^2 - y^2$ = write the real value---------(1)
$2xy$ = write the imaginary  value------(2)
from equation (1) and (2)
$x^2 + y^2 = \sqrt{(x^2 - y^2)^2 +  4x^2y^2}$
you will get $x^2 + y^2 = ?$ -------(3)
from equation (1) and (3)
you will get the value of $x$ and $y$
