Let f(x)=(x+3)/(x-1)
Let's build the sign chart
color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaaa)-3color(white)(aaaaaaa)1color(white)(aaaa)+oo
color(white)(aaaa)x+3color(white)(aaaaa)-color(white)(aaa)0color(white)(aaa)+color(white)(aaaaa)+
color(white)(aaaa)x-1color(white)(aaaaa)-color(white)(aaa)#color(white)(aaaa)-#color(white)(aa)||color(white)(aa)+
color(white)(aaaa)f(x)color(white)(aaaaaa)+color(white)(aaa)0color(white)(aaa)-color(white)(aa)||color(white)(aa)+
Therefore,
f(x)>=0, when x in (-oo,-3] uu(1,+oo)
graph{(x+3)/(x-1) [-16.02, 16.01, -8.01, 8.01]}