simplifying equation with radicals

Hello Im working on some problems and have come into a problem understanding how something is simplified.
The problem I am working on starts with -(1/2)^2+1=X^2
which was simplified to 3^.5/2=X
Can someone please tell me how this was done it would be very helpful thanks in advance.

$\displaystyle x^2=1-\frac{1}{4}$

$\displaystyle x^2=\frac{3}{4}$

$\displaystyle x_{1,2}=\pm \frac{\sqrt 3}{2}$

Thanks that seems so obvious now