A potential energy function for system $1$ is given by U$1($x$)=$Cx$2+$Bx$3$U$1($x$)=$Cx$2+$Bx$3.$ The potential energy function for system $2$ is given by U$2($x$)=$A$+$Cx$2+$Bx$3$U$2($x$)=$A$+$Cx$2+$Bx$3,$ where AA is a positive quantity. How does the force on system $1$ relate to the force on system $2$ at a given position?