不懂這題PS要怎麼解?

wealthylun

For which of the following functions is f(a + b) = f(a) + f(b) for all positive numbers a and b ?

(A) f(x) = x 2

(B) f(x) = x + 1

(C) f(x) =√x

(D) f(x) = 2/x

(E) f(x) = -3x



答案是 E


(A) f(x) = x 2

(B) f(x) = x + 1

(C) f(x) =√x

(D) f(x) = 2/x

(E) f(x) = -3x



答案是 E

wandaonion

题目中问的相当于可以把两个拆开的呀 楼主带一下就好了啊 f(a+b)=-3（a+b)=-3a+(-3)b=f(a)+f(b)
刚开始以为A是X乘以2呢 还在想怎么两个答案 A选项应该是X的平方吧

wealthylun

謝謝你了