A-B
=x^n＋x^(-n)-x^(n-1)-x^(1-n)
=x^(n-1)*(x-1)+x^(-n)*(1-x)
=(x-1)*x^(-n)*(x^(2n-1)-1)
由于当x为正实数且n为自然数
2n-1》=1
i）当x>1时
x-1>0 x^(-n)>0
x^(2n-1)>1
x^(2n-1)-1>0
A-B>0
ii）当x=1时
x-1=0
A-B=0
iii）当0