I don't know exactly what level you are in, but the obvious factors are
y = 2x*(x^3 + 11x + 30)
This gives one more factor somewhere around x = -11.3 . Notice that the minimum is around - 3000 or so. I don't think anyone is going to try and take this any further. My calculator figures out cubics and gives an answer of -11.23. There are two other roots but they are a complex pair.
