How do you solve x^2+x-6<0x2+x6<0 using a sign chart?

1 Answer
Jan 15, 2017

The answer is x in ] -3,2 [x]3,2[

Explanation:

Let's factorise the expression,

x^2+x-6=(x-2)(x+3)x2+x6=(x2)(x+3)

and let f(x)=x^2+x-6f(x)=x2+x6

Now we can do the sign chart

color(white)(aaaa)aaaaxxcolor(white)(aaaa)aaaa-oocolor(white)(aaaa)aaaa-33color(white)(aaaaa)aaaaa22color(white)(aaaa)aaaa+oo+

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

color(white)(aaaa)aaaax-2x2color(white)(aaaaa)aaaaa-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++

Therefore,

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