Question

Let $A=\{1,2,3\}$ and $B=\{1,4,7,12,15,18\}$. A function $f:A\to B$ is defined by $f\left(x\right)=x^2+3$. Then

• A. range of $f$ is $\{4,7,12\}$
• B. range of $f$ is $\{1,4,7,12\}$
• C. co-domain of $f$ is $\{4,7,12\}$
• D. co-domain of $f$ is $\{1,4,7,12,15,18\}$

Answer 1

Answer: (A), (D)

co-domain of $f$ is $\{1,4,7,12,15,18\}$

Domain of $f$ is $\{1,2,3\}$
Co-domain of $f$ is $\{1,4,7,12,15,18\}$

$f\left(x\right)=x^2+3$
$f\left(1\right)=1+3=4$
$f\left(2\right)=4+3=7$
$f\left(3\right)=9+3=12$
$\therefore$ Range of $f$ is $\{4,7,12\}$