Question 1005153
you are told the zeroes, so you need to start with that
{{{f(x) = (x+1)(x-3)(x-4)}}}

Now start to expand
{{{f(x) = (x^2 -3x + x -3)(x-4)}}}
{{{f(x) = (x^2 -2x -3)(x-4)}}}
{{{f(x) = x^3 -4x^2 -2x^2 + 8x -3x + 12}}}
{{{f(x) = x^3 - 6x^2 + 5x + 12}}}

See the entire solution here --> http://www.wolframalpha.com/input/?i=%28x%2B1%29%28x-3%29%28x-4%29&dataset=