[問題]GWD2-14

[blacklilu]

The function f is defined by f(x) = - 1/x for all nonzero numbers x. If f(a) = - 1/2 and f(ab) = 1/6, then b =

A. 3
B. 1/3
C. - 1/3
D. -3
E. -12

Ans : D

偶又哪算錯了.... :'(

[marco]

f(x)=-1/x
f(a)=-(1/a)=-(1/2)故a=2
f(ab)=-(1/ab)=1/6
a=2帶入,則-(1/2b)=1/6
故b=-3

[Quinton]

這題只要細心就行∼

雖然我第一次作也作錯∼真的覺得在時間緊迫的壓力下∼要答題粉困難！