$21-26$ Sketch a possible graph for a function $f$ with the specified properties. $($Many different solutions are possible.$)$

$21.($i$)$ the domain of $f$ is $-1,1$

$($ii$)f(-1)=f(0)=f(1)=0$

$($iii$)\underset{x-1^{+}}{lim}f(x)=\underset{x0}{lim}f(x)=\underset{x{1}^{-}}{lim}f(x)=1$