Question 349256
Square roots of negative numbers are called imaginary 
numbers. A complex number has an imaginary part
which includes {{{sqrt(-1)}}} and a real part which is
just an ordinary number. 
The complex numbers are plotted on what is called the 
complex plane. If this is too much, just remember
{{{i = sqrt(-1)}}}
{{{i^2 = -1}}}
{{{i^3 = -sqrt(-1)}}}
{{{i^4 = +1}}}
and this cycle just repeats over and over
You can turn any square root of a negative number
into a number times {{{sqrt(-1)}}}, as follows:
{{{sqrt(-47) = sqrt(47)*sqrt(-1)}}}
{{{ sqrt(47)*sqrt(-1) = sqrt(47)*i}}}
or
{{{sqrt(-81) = 3*sqrt(-1)}}}
{{{3*sqrt(-1) = 3i}}}