Remember that for any quadratic equation:
ax^2+bx+c = 0
The quadratic formula says that the two solutions will be:
x = -b/2a ± sqrt(b^2-4ac)/2a
What are a, b and c in this case?
Try substituting in the numbers from your problem and seeing if you can work it out. If you have trouble let me know and I will do my best to help.