Answer
$f(x)=x^3-18x^2+107x-210$
Work Step by Step
RECALL:
If $a$ is a zero of a polynomial, then $x-a$ is a factor of the polynomial.
Thus, having x=5, 6, 7 as zeros of the polynomial function means that $x-5, x-6$, and $x-7$ are factors of the polynomial.
Therefore the function is
$f(x)=(x-5)(x-6)(x-7)
\\f(x)=x^3-18x^2+107x-210.$