How do you solve (3x+6)/(2x-12)<=0 using a sign chart?

1 Answer
Nov 3, 2017

The solution is x in [-2,6)

Explanation:

Let f(x)=(3x+6)/(2x-12)=(3(x+2))/(2(x-6))

Let's build the sign chart

color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaaaa)-2color(white)(aaaaaaa)6color(white)(aaaaaa)+oo

color(white)(aaaa)x+2color(white)(aaaaaa)-color(white)(aaa)0color(white)(aaa)+color(white)(aaaaaa)+

color(white)(aaaa)x-6color(white)(aaaaaa)-color(white)(aaa)0color(white)(aaa)-color(white)(aa)||color(white)(aaa)+

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

Therefore,

f(x)<=0 when x in [-2,6)

graph{(3x+6)/(2x-12) [-22.8, 22.83, -11.4, 11.4]}