Question

Let $A=\{1,2,3\}$ and $B=\{2,4,6,8\}$. Consider the rule $f : A \rightarrow B , f ( x )=2 x \forall x \in A .$ The domain, codomain and range of $f$ respectively are

• A. $\{1,2,3\},\{2,4,6\},\{2,4,6,8\}$
• B. $\{1,2,3\},\{2,4,6,8\},\{2,4,6\}$
• C. $\{2,4,6,8\},\{2,4,6,7\},\{1,2,3\}$
• D. $\{2,4,6\},\{2,4,6,8\},\{1,2,3\}$

Answer 1

Answer: (B)

Given, $f ( x )=2 x , \forall x \in A$

Value of function at $x =1, f (1)=2(1)=2$
Value of function at $x=2, f(2)=2(2)=4$
Value of function at $x=3, f(3)=2(3)=6$
Domain of $f =\{1,2,3\} ;$
Codomain of $f =\{2,4,6,8\}$
Range of $f =\{2,4,6\}$