The graph of $\displaystyle {f{{\left({x}\right)}}}={2}{x}^{{3}}+{9}{x}^{{2}}-{60}{x}+{10}$ has two horizontal tangents. One occurs at a negative value of $\displaystyle {x}$ and the other at a positive value of $\displaystyle {x}$. What is the negative value of $\displaystyle {x}$ where a horizontal tangent occurs? Preview Question 6 Part 1 of 2  


What is the positive value of $\displaystyle {x}$ where a horizontal tangent occurs? Preview Question 6 Part 2 of 2