What is the square root of one minus four divided by two?

It is -1.22474487 and a bar over .22474487

square root of one minus four divided by two?''

\(\sqrt{1-4/2} = \sqrt{1-2}=\sqrt{-1}=i\)

This is an imaginary number.  There is no real number solution.

Nothing multiplied by itself = a negative number in the real number system.