How do you solve (x+8)(x+2)(x-3)>=0(x+8)(x+2)(x3)0 using a sign chart?

1 Answer
Dec 19, 2016

The answer is x in [-8,-2] uu [3, +oo[ x[8,2][3,+[

Explanation:

Let f(x)=(x+8)(x+2)(x-3)f(x)=(x+8)(x+2)(x3)

Let's do the sign chart

color(white)(aaaa)aaaaxxcolor(white)(aaaa)aaaa-oocolor(white)(aaaa)aaaa-88color(white)(aaaa)aaaa-22color(white)(aaaa)aaaa33color(white)(aaaa)aaaa+oo+

color(white)(aaaa)aaaax+8x+8color(white)(aaaaa)aaaaa-color(white)(aaaa)aaaa++color(white)(aaaa)aaaa++color(white)(aaaa)aaaa++

color(white)(aaaa)aaaax+2x+2color(white)(aaaaa)aaaaa-color(white)(aaaa)aaaa-color(white)(aaaa)aaaa++color(white)(aaaa)aaaa++

color(white)(aaaa)aaaax-3x3color(white)(aaaaa)aaaaa-color(white)(aaaa)aaaa-color(white)(aaaa)aaaa-color(white)(aaaa)aaaa++

color(white)(aaaa)aaaaf(x)f(x)color(white)(aaaaaa)aaaaaa-color(white)(aaaa)aaaa++color(white)(aaaa)aaaa-color(white)(aaaa)aaaa++

Therefore,

f(x)>=0f(x)0, when x in [-8,-2] uu [3, +oo[ x[8,2][3,+[

graph{(x+8)(x+2)(x-3) [-154.2, 146, -60.4, 89.8]}