Let's do the long division #color(white)(aaa)##3x^3-5x^2+10x+4##color(white)(aaa)##∣##3x+1# #color(white)(aaa)##3x^3+x^2##color(white)(aaaaaaaaaaaaa)##∣##x^2-2x+4# #color(white)(aaaa)##0-6x^2+10x# #color(white)(aaaaaaa)##-6x^2-2x# #color(white)(aaaaaaaaaa)##0+12x+4# #color(white)(aaaaaaaaaaaa)##+12x+4# #color(white)(aaaaaaaaaaaaaa)##+0+0#