The roots of the function is equal to x-coordinate of the points at which curve intersect the x-axis.
Plot the equation y=x^3+2x^2-5x-10 on the graph.
The graph interset the x-axis at point (-2.236,0); (-2,0) and (2.236,0). So zeros of the function is,
x = - 2.236,
x = -2, and
x = 2.236.