Let f(x)=(x^2+5x)/(x-3)=(x(x+5))/(x-3)
The domain of f(x) is D_f(x)=RR-{3}
Let's do the sign chart
color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaa)-5color(white)(aaaaa)0color(white)(aaaaaaaaa)3color(white)(aaaaa)+oo
color(white)(aaaa)x+5color(white)(aaaaa)-color(white)(aaaa)+color(white)(aaaaa)+color(white)(aaaa)color(red)(∥)color(white)(aa)+
color(white)(aaaa)xcolor(white)(aaaaaaaa)-color(white)(aaaa)-color(white)(aaaaa)+color(white)(aaaa)color(red)(∥)color(white)(aa)+
color(white)(aaaa)x-3color(white)(aaaaa)-color(white)(aaaa)-color(white)(aaaaa)-color(white)(aaaa)color(red)(∥)color(white)(aa)+
color(white)(aaaa)f(x)color(white)(aaaaaa)-color(white)(aaaa)+color(white)(aaaaa)-color(white)(aaaa)color(red)(∥)color(white)(aa)+
Therefore,
f(x)>=0, when x in [-5,0 ] uu ] 3, +oo [