How do you solve (x-1)(x-2)(x-3)>=0 using a sign chart?

1 Answer
Jan 2, 2017

The answer is x in [1 ,2 ] uu [3, +oo [

Explanation:

Let f(x)=(x-1)(x-2)(x-3)

Now, we can establish the sign chart

color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaaa)1color(white)(aaaaaa)2color(white)(aaaaaaa)3color(white)(aaaaaa)-oo

color(white)(aaaa)x-1color(white)(aaaaa)-color(white)(aaaaa)+color(white)(aaaaa)+color(white)(aaaaa)+

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

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

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

Therefore,

f(x)>=0 when x in [1 ,2 ] uu [3, +oo [