Negative discriminants?

[Dillinger4]

Im starting to understand 2nd polynominals better except when the discriminant is negative. I took this equation 4x^2 + 6 + 17 = 0 and evaluated the discriminant whis came out to be negative.
sqr(6^2 - 4 * 4 * 17) = sqr(-146) Now judging by the quardratic equation i think i set up the problem like this. -6 +/- sqr(-146) / 8.
which i think should be. -6 +/- 12i / 8

S={-0.75,1.5i, 0.75, 1.5i}

Does this look at all right. Am i at least on the right track?