How do you solve 3/(x+1)<=3 using a sign chart?

1 Answer
Jun 22, 2017

The solution is x in (-oo,-1) uu [0,+oo)

Explanation:

We cannot do crossing over

Let's rearrange the inequality

3/(x+1)<=3

3/(x+1)-3<=0

(3-3x-3)/(x+1)<=0

(-3x)/(x+1)<=0

Let f(x)=(-3x)/(x+1)

Let's build the sign chart

color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaaaa)-1color(white)(aaaaaaaa)0color(white)(aaaaa)+oo

color(white)(aaaa)-3xcolor(white)(aaaaaa)+color(white)(aaaa)||color(white)(aaaa)+color(white)(aa)0color(white)(aa)-

color(white)(aaaa)x+1color(white)(aaaaa)-color(white)(aaaa)||color(white)(aaaa)+color(white)(aa)0color(white)(aa)+

color(white)(aaaa)f(x)color(white)(aaaaaa)-color(white)(aaaa)||color(white)(aaaa)+color(white)(aa)0color(white)(aa)-

Therefore,

f(x)<=0 when x in (-oo,-1) uu [0,+oo) graph{3/(x+1)-3 [-19.3, 21.26, -12.45, 7.82]}