Graph

The points where it crosses the x  axis  will give solutions to the polynimial function .

The graph crosses the x  - axis at a point that would suggest a factor.

It crosses the x  - axis at one point hence there are one real root.

x  = -4.20259, -1.33031

Use synthatic division to detrmine if the given values of x  are roots of the polynomial.

Since f (-4.20259) = 0,   x  =  -4.20259 is a zero.

Since f (-1.33031) = 0,   x = -1.33031 is a zero.