Note that f is continuous on $($$,6)$ and $(6,$ $).$ For the function to be continuous on $($$,$ $),$ we need to ensure that as x approaches $6,$ the left and right limits match.

First we find the left limit$.$

lim$$x$6$f$($x$)=$lim$$x$6($cx$2+5$x$)=$

Next, we find the right limit$.$

lim$$x$6+$f$($x$)=$lim$$x$6+($x$3$ cx$)=$