(1-(|x|-1)^2)^0.5=-2.5(1-(|x|/2)^0.5)^0.5 - Wolfram|Alpha http://www.wolframalpha.com/input/?i=%281-%28%7Cx%7C-1%29^2%29^0.5%3D-2.5%281-%28%7Cx%7C%2F2%29^0.5%29^0.5