Question

how do you write sqrt of -5 in form of bi where b is the real number?

Answer 1

\[\large \sqrt{-5}=\sqrt{-1*5}=\sqrt{-1}\sqrt{5}=i\sqrt{5}=\sqrt{5}i\]
So \[\large \sqrt{-5}=\sqrt{5}i\]

Answer 2

@smurfy note that the 'i" is outside of the radical, not inside!