For the following question, I am getting that the Fixed points are u=0 and $u_{+/-}=(1/r +/- \sqrt(1/r^2 -4))/2 $. Then I see that $u_{+/-} $ is real for r^2<1/4 => r>1/2. In this evaluation I am not sure where to get the value $r_{c} $ from as required in the underlined bit of the text.
Any help would be much appreciated!
