Question

If $f:N\to R$ is a function defined as $f\left(x\right)=2x^2+1$, then the image of $5$ under $f$ is

Answer 1

Here, $f\left(x\right)=2x^2+1$
Put $x=5$ in $f\left(x\right)$, we get
$f\left(5\right)=2(5{)}^2+1$
$\Rightarrow f\left(5\right)=51$
Image of $5$ under $f$ is $51.$