There are 3 parts to this answer. A) list all rational zeros that are possible according to the rational zero theorem

we have the function
f(x)=x^3-3x^2-4x+12
p=12 ----> constant term
q=1 ---> leading coefficient
so
p/q=(+-1,+-2,+-3,+-4,+-6,+-12)/(+-1)
All possible rational zeros, according to the Rational Zero Theorem, are
-1,-2,-3,-4,-6,-12,1,2,3,4,6,12