The potential energy function for a system of particles is given by

U$($x$)=6$x$3+9$x$2+8$x$,$

where x is the position of one particle in the system.

$($a$)$

Determine the force Fx on the particle as a function of x$.$

Fx $=$

$($b$)$

For what values of x is the force equal to zero? $($Enter your answers from smallest to largest.$)$

x$=$x$=$