函数y=3x2-1（x≥-1）的反函数是（） A．y=(x+1)3(x≥-1)B_爱下问搜题

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问题选择题

函数y=

3	x2

-1（x≥-1）的反函数是（　　）

A．y=

(x+1)3

(x≥-1)

B．y=-

(x+1)3

(x≥-1)

C．y=

(x+1)3

(x≥0)

D．y=-

(x+1)3

(x≥0)

答案

∵函数y=

3	x2

-1（x≥-1），y≥-1，

∴x²=（y+1）³，故 x=-

(y+1)3

，

故反函数为 y=-

(x+1)3

(x≥-1)，

故选B．

选择题

---Have you cooked supper_________?

---Yes, I have _________ finished it.

A．yet, just

B．yet, ever

C．already, yet

D．already, just

选择题

A lot of trees ______ on the hill yesterday. [ ]

A. are planted

B. will be planted

C. have been planted

D. were planted