[問題]GWD 1-9

[Ally]

Q9:
For all integers n, the function f is defined by f (n) = a的n平方, where a is a constant. What is the value of f (1)?
(1) f (2) = 100
(2) f (3) = -1,000
答案給B
為什麼不是D?

[魚]

(1) f (2) = 100 =A^2

A=+/- 10 ......非唯一 ;)

[cocaine]

f(n)=a^n,題目要問f(1)=a,a多少??

(1)f(2)=a^2=(10)^2=(-10)^2
a=10 or -10

(2)f(3)=a^3=(-10)^3
a=-10

ans:B