Let's perform the synthetic division
Let #f(x)=3x^4-2x^3+5x^2-4x-2#
Let's perform the synthetic division
#color(white)(aaaa)##-1##color(white)(aaaaa)##|##color(white)(aaaa)##3##color(white)(aaaaaa)##-2##color(white)(aaaaaa)##5##color(white)(aaaaa)##-4##color(white)(aaaaa)##-2#
#color(white)(aaaaaaaaaaaa)#_________
#color(white)(aaaa)##color(white)(aaaaaaa)##|##color(white)(aaaa)##color(white)(aaaaaaa)##-3##color(white)(aaaaaaa)##5##color(white)(aaaaa)##-10##color(white)(aaaa)##14#
#color(white)(aaaaaaaaaaaa)#________
#color(white)(aaaa)##color(white)(aaaaaaa)##|##color(white)(aaaa)##3##color(white)(aaaaaa)##-5##color(white)(aaaaaaa)##10##color(white)(aaaa)##-14##color(white)(aaaaa)##color(red)(12)#
#f(x)=(3x^3-5x^2+10x-14)+12/(x+1)#
The remainder is #=-2#