a分之(x-b) -2 = b分之(x-a) 两边乘ab
b(x-b)-2ab=a(x-a)
bx-b²-2ab=ax-a²
ax-bx=a²-b²-2ab
(a-b)x=a²-b²-2ab
x=(a²-b²-2ab)/(a-b)