Polynomials in the fourth degree are called quartic equations. In solving the roots of polynomials, there are techniques available. For quadratic equations, you use the quadratic formula. For cubic equations, you use the scientific calculator. But for quartic equations and higher, it is very complex. The method is very lengthy and can get very messy because you introduce a lot variables. So, I suggest you do the easiest method to estimate the roots.
Graph the equation by plotting arbitrary points. The graph looks like that in the figure. The points at which the curve passes the x-axis are the solution which are encircled in red.In approximation, the rational roots or zero's are
-3.73, -1, -0.28 and 2.
Answer:
1, 500km
Step-by-step explanation:

The minimum of a graph is where the curve of the parabola is at its lowest point. On this graph the minimum looks to be at (-2, -2), but make sure that is where the curve is lowest.