How do you solve ((x+7)(x-3))/(x-1)>=0?

1 Answer
Feb 3, 2017

The answer is x in [-7,1 [ uu [3,+oo[

Explanation:

Let f(x)=((x+7)(x-3))/(x-1)

The domain of f(x) is D_f(x)=RR-{1}

Now we can build the sign chart

color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaa)-7color(white)(aaaaaaa)1color(white)(aaaaaa)3color(white)(aaaaaa)+oo

color(white)(aaaa)x+7color(white)(aaaaa)-color(white)(aaaa)+color(white)(aaaa)||color(white)(aa)+color(white)(aaaa)+

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

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

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

Therefore,

f(x)>=0 when x in [-7,1 [ uu [3,+oo[