Find the roots in simplest a+bi form y=2x^2-4x+5

[tex]\frac{-b+-\sqrt{ b^2-4ac}}{2a}[/tex]

[tex]\frac{4+-\sqrt{16-4(2)(5)}}{2(2)}[/tex]

[tex]\frac{4+-\sqrt{24}}{4}[/tex]

to put in a+bi form I believe that that it has to be a perfect square and that I can not have a radical in the answer? Please help with what I am missing Thanks