#(x+2)=0 rarr x=color(red)((-2))#
Synthetic division by #(x+2)# is equivalent to synthetic substitution with #x=color(red)((-2))#
#{:(,,color(grey)x^4,color(grey)x^3,color(white)("xx")color(grey)x^2,color(white)("x")color(grey)x^1,color(white)("xx")color(grey)x^0),
(," | ",-3,0,color(white)("xx")0,color(white)("x")0,color(white)("xx")0),
(ul(+color(white)("x"))," | ",ul(color(white)("Xx")),ul(6),ul(-12),ul(24),ul(-48)),
(xxcolor(red)((-2))," | ",-3,6,-12,24,-48),
(,,color(grey)(x^3),color(grey)(x^2),color(white)("x")color(grey)(x^1),color(grey)(x^0),color(grey)R)
:}#