Please do this work yourself. If, after having arrived at an answer of your own, check it using Wolfram or some other site.
Here I'd use the quadratic formula:
-(4) plus or minus sqrt( (4)^2 - 4(1)(6) )
x = -----------------------------------------------------
2
4 plus or minus sqrt(16-24)
= ---------------------------------------
2
4 plus or minus i*sqrt(8)
= -----------------------------------
2
and so on. Remember that sqrt(8) = 2sqrt(2).