x^3-5x^2+x-5x3−5x2+x−5 can be factored as
color(white)("XXX")color(red)(""(x^3+x))-color(blue)(""(5x^2+5))XXX(x3+x)−(5x2+5)
color(white)("XXX")=color(red)(x(x^2+1))-color(blue)(5(x^2+1)XXX=x(x2+1)−5(x2+1)
color(white)("XXX")=(color(red)(x)-color(blue)(5))*(x^2+1)XXX=(x−5)⋅(x2+1)
For the zeroes:
either
color(white)("XXX")(x-5)=0color(white)("XX")rarrcolor(white)("XX")x=5XXX(x−5)=0XX→XXx=5
or
color(white)("XXX")(x^2+1)=0color(white)("XX")rarrcolor(white)("XX")x=+-sqrt(-1)=+-iXXX(x2+1)=0XX→XXx=±√−1=±i