-(-6)+/-√-6^2-(4*2*3)
This could mean manz different things, but if this is what you intend ....
\(-(-6) \pm \sqrt{-6^2-(4*2*3)}\\ =+6 \pm \sqrt{-36-24}\\ =6 \pm \sqrt{-60}\\\)
There are no REAL solutions to this as yu cannot find the square root of a negative number.
The complex solutions are
\(=6\pm\sqrt{60}\;i\\ =6\pm2\sqrt{15}\;i\)