[問題]GWD29-3

[kuanchen]

If n is an interger and x^n - x^(-n) = 0, what is the value of x?
(1) x is an interger
(2) n not equal to 0

the answer is E.... can somebody tell me why? I think B is sufficient....

[StanleyHuang]

x[sup]n[/sup] - x[sup]-n[/sup]=(x[sup]2n[/sup]-1) / x[sup]n[/sup] = (x[sup]n[/sup]+1)(x[sup]n[/sup]-1) / x[sup]n[/sup] = 0
可得 x[sup]n[/sup] = 1 or -1

由 1[sup]1[/sup]=1, (-1)[sup]1[/sup]=-1 可知答案為(E)

[amyliang]

有看沒有懂????