Finding the zeroes of a function?

Question

how do i find the zeroes of this function.
f(x) = x^3 - 2x^2 - 4x

How do I solve this

Answer 1

x^3 - 2x^2 - 4x = y

x^3 -1 ( 2x^2 + 4x ) = y
x^3 - (2) (x^2 + 2x ) = y

I think It's called rational roots theorem

I used a graphing calculator and One is (0,0)

x = 1 + square root of 5 and one minus the square root of 5

so on a graph approx (-1.2360679, 0) and (3.23606, 0)

Answer 2

Set x^3-2x^2-4x = 0
now factor it. note that x is a common factor
x(x^2-2x-4) = 0
from this you can see that x=0 is one of the zeroes of the function

The other zeroes would be when x^2-2x-4=0
Solve this using the quadrtaic formula.
You get 3 solutions which works for a cubic polynomial.

Answer 3

Factor
yeah i see the first poster covered it