Question

If $f:N\to R$ is a function defined as $f\left(x\right)=2x^2+1$, then the preimage of $9$ is

Answer 1

Here, $f\left(x\right)=2x^2+1$
$f\left(x\right)=9$
$\Rightarrow 9=2x^2+1$
$\Rightarrow 8=2x^2$
$\Rightarrow 4=x^2$
$\Rightarrow x=-2,2$
But $x\in N$
$\therefore x=2$
Preimage of $9$ is $2.$