✔ 最佳答案
Sol
p=a/b
1/a-1/b-1/(a+b)=0
b(a+b)-a(a+b)-ab=0
ab+b^2-a^2-ab-ab=0
-a^2-ab+b^2=0
a^2+ab-b^2=0
(a/b)^2+(a/b)-1=0
p^2+p-1=0
p^2=1-p
p^3=p-p^2=p-(1-p)=2p-1
p^6=4p^2-4p+1=4(1-p)-4p+1=5-8p
(a/b)^3-(b/a)^3
=p^3-1/p^3
=(p^6-1)/p^3
=(4-8p)/(2p-1)
=-4
/