Consider the given equation as,
Equate the function to zero,
Since it is a cubic solution, we have to find the first zero using Hit and Trial Method,
It is found that x=-2 is a zero of the cubic equation, it implies that(x+2) must be a factor of the polynomial.
So we can use the Long Division to find the other two zeroes as follows.
Thus, by the long division we obtained that,
Equating the terms to zero,
We already know the zero x= -2, the other two zeroes can be obtained from the other quadratic factor,
Thus, the remaining two zeroes are 1.63 and -1.38 approximately.
So it concludes that the given cubic polynomial has the zeroes as -1.38, 1.63, and -2.