What is the square root of negative twelve?

Please note that Geno's answer is an imaginary number.

there are NO REAL SOLUTIONS for this.   There is no REAL answers to the square root of a negative number.

√(-12)  =  √(4 x 3 x -1)  =  √(4) x √(3) x √(-1)

√(4)  =  2

√(-1)  can be replaced with the symbol  i:

   =  2√(3)i  or  2i√(3)