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

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Answer 1 · 2016-03-22T19:44:59

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

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

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

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

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

$x=6 or x=-1$

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