Question

Let $A=\{1$, $2$, $3\}$ and $B=\{2$, $4$, $6$, $8\}$.
Consider the rule $f:A\to B$, $f\left(x\right)=2x\forall x\in A$. The domain, co-domain 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, $f(x)=2x$, $\forall x\in A$
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 $f=\{1$, $2$, $3\}$
Co-domain of $f=\{2$, $4$, $6$, $8\}$
Range of $f=\{2$, $4$, $6\}$