Determine the values of $x\in (-3,3)$ at which $f$ is not differentiable using the following graph:

For what value or values of the constant $k$, if any, is the function $g\left(x\right)$ defined as , continuous at $x=0$ and differentiable at $x=0$?

Determine whether the following piecewise function is differentiable at $x=0$.

Calculate the value of $b$ that makes the function differentiable everywhere.