Discussion Forum



1)

If the range of the function f(x)=-3x-3 is (3,-6,-9,-18) , them which of the following elements is not in the domain of f?


A) -1

B) -2

C) 1

D) 2

Answer:

Option A

Explanation:

 We have ,f(x)=-3x-3

(i)  let f(x)=3 , then we get

         $ 3=-3x-3 \Rightarrow 6=-3x \Rightarrow x=-2$

 (ii)    Let f(x)=-6 , then we get

              $ -6=-3x-3 \Rightarrow -3=-3x \Rightarrow x=1$

(iii)  let f(x)=-9 , then we get

$ -9=-3x-3 \Rightarrow -6=-3x \Rightarrow x=2$

(iv) Let f(x)=-18, then we get

$ -18=-3x-3 \Rightarrow -15=-3x \Rightarrow x=5$

Thus, domain of f={-2,1,2,5}

Hence,-1 cannot  be in the domain of f.