Question 825417
List the possible rational zeros the function 
f(x) =  3x^3 - 21x + 18
Form: x = p/q
p = +-1,+-2,+-3,+-6,+-9,+-18
q = +-1,+-3
---
p/q = +-1,+-2,+-3 etc,etc
==================================

Describe and use one method (other than substitution) to determine if x = 6 is a zero of f(x).
Using synthetic division::
6)....3....0....-21....18
......3...18....33...|..216

Since the remainder is not zero, x = 6 is not a zero of f(x).

============================

 Then find all the real zeros of the function.
Using synthetic division:: x = 1,2,-3
===================
Cheers,
Stan H.