2x -2 + r ^ 2 = > (2x - 2 + r) * (2x - 2 + r) = 4x^2 - 4x + 2rx - 4x + 4 - 2rx + 2rx - 2r + r^2 =

4x^2 - 8x + 2rx + 4 - 2r = 4x^2 - 2x*(4 - r) + 2*(2 - r)

4x^2 - x*(8 - 2r) + (4 - 2r + r^2) = 0

D = b^2 - 4ac = (2r - 8)^2 - 4*(4 - 2r + r^2) = 4r^2 - 32r + 64 - 32 + 16r - 4r^2 = 16r - 32


(2r - 8) +- sqr(16r - 32) / 8 = (2r - 8) +- 4sqrt(r-2) / 8




x1 = ((2r - 8) + 4sqrt(r-2)) / 8
x2 = ((2r - 8) - 4sqrt(r-2)) / 8