x1 = 3/4 y1 = -4/3
x2 = -1/3 y2 = 3
x3 = 4 y3 = -1/4
x4 = 3/4,y 4 = -4/3
所以
x7 = x4 = x1
y2008 = y (3*669 + 1) = y1 = -4/3