How do you solve 3/(x-2)<=3/(x+3) using a sign chart?

1 Answer
Feb 19, 2017

The solution is x in ]-3,2[

Explanation:

We cannot do crossing over, so rewrite the inequality

3/(x-2)<=3/(x+3)

3/(x-2)-3/(x+3)<=0

Placing on the same denominator

(3(x+3)-3(x-2))/((x-2)(x+3))<=0

(3x+9-3x+6)/((x-2)(x+3))<=0

15/((x-2)(x+3))<=0

Let f(x)=15/((x-2)(x+3))

The domain of f(x) is D_f(x)=RR-{-3,2}

Now, we can build the sign chart

color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaaa)-3color(white)(aaaaaa)2color(white)(aaaaaaa)+oo

color(white)(aaaa)x+3color(white)(aaaa)-color(white)(aaaa)||color(white)(aa)+color(white)(aa)||color(white)(aaaa)+

color(white)(aaaa)x-2color(white)(aaaa)-color(white)(aaaa)||color(white)(aa)-color(white)(aa)||color(white)(aaaa)+

color(white)(aaaa)f(x)color(white)(aaaaa)+color(white)(aaaa)||color(white)(aa)-color(white)(aa)||color(white)(aaaa)+

Therefore,

f(x)<=0 when x in ]-3,2[