Question 141581
{{{f(x)=x^3+3x^2-4x}}}
{{{f(-4)=(-4)^3+3(-4)^2-4(-4)}}}
{{{f(-4)=-64+48+16}}}
{{{f(-4)=0}}}
x=-4 is a zero of f(x). 
{{{f(2)=2^3+3(2)^2-4(2)}}}
{{{f(2)=8+12-8}}}
{{{f(2)=12}}}
x=2 is not a zero of f(x).
{{{f(1)=1^3+3(1)^2-4(1)}}}
{{{f(1)=1+3-4}}}
{{{f(1)=0}}}
x=1 is a zero of f(x).