Question

How do you find all the zeros of `f(x) = x^3 - 2x^2- 21x -18` with -3 as a zero?

Answer 1

First divide the polynom by x+3 and calculate the solutions with the quadratic formula.

Explanation:

`(x^3-2x^2-21x-18)/(x+3)=x^2-5x-6`

`x=(5+-sqrt(5^2-4*1*(-6)))/2`

`x=(5+-sqrt(49))/2`

`x=(5+-7)/2`

`x=6 or x=-1`