Skag55 wrote:

b-6 <0 => b<6 and b+2<0 => b <-2

Is this wrong?

Yes,but only the highlighted part. Note that if a*b<0, then a and b have to be of opposite signs.

If you apply that to the above inequality, you would get the same range as Bunuel got.

So yes, your method is also correct.

Aha, so I need to elaborate more on the equation then, i.e. each term will have 2 solutions like:

and same for the other term.