121(x-1)的平方=64
(x-1)^2=64/121
x-1=8/11 或 x-1=-8/11
x=19/11 或 x=3/11
y^3+8=0
y^3=-8
y=-2
x-y= 19/11+2=31/11
或 3/11+2＝25/11