actually, not sure if it belongs into this group:

I have the following problem with the cubic equation:

20x^3+8^2+7x+6=0

Is there some kind of cubic equation (just as the quadratic one)? According to wikipedia there, is:

http://en.wikipedia.org/wiki/Cubic_function

(under the title: "critical points of a cubic function")

So I tried to apply it just like the quadratic function. Sadly, my root-funtion turns out to be negative:

the square root of: 8^2-3*20*7 --> negative, so not possible

what am I doing wrong??

would really appreciate if sbdy could help!!!