Factor $f(x)$ into linear factors given that $k$ is a zero of $f(x)$. 8) $f(x)=x^{3}-2 x^{2}-36 x+72 ; k=6$

Step 1 ：Given that $k=6$ is a zero of $f(x)$, we can say that $(x-6)$ is a factor of $f(x)$ according to the Factor Theorem.

Step 2 ：Next, we perform polynomial division of $f(x)$ by $(x-6)$ to find the other factors of $f(x)$.

Step 3 ：Finally, we factorize the quotient obtained from the polynomial division to get the linear factors of $f(x)$.

Step 4 ：The linear factors of $f(x)$ are \(\boxed{(x-6)}, \boxed{(x-2)}, \boxed{(x+6)}\).