Question

$A:\{-1,0,2,5,6,11\},B=\{2,-1,1,0,11,108\}$ and $f\left(x\right)=x^2-x-2,$ then $f:A\to B$ is

• A. a function
• B. a one-one function
• C. an onto function
• D. not a function

Answer 1

The correct option is D not a function

$f(-1)=(-1{)}^2-(-1)-2$
$=+1+1-2$
$=0$
$f\left(0\right)=-2$
$f\left(2\right)-2^2-2-2$
$=0$
$f\left(5\right)=5^2-5-2$
$=18$
$f\left(6\right)=36-6-2$
$-28$ $\notin B$
$f\left(11\right)={11}^2-11-2$
$=108$
Range of $f\left(x\right)$ does not lie in its codomain.
$\therefore f\left(x\right)$ is not a function.