Which of the following functions is not differentiable in the domain $[-1,1]$ ?
(a) $f(x) = x^2$
(b) $f(x) = x-1$
(c) $f(x) = 2$
(d) $f(x) = Maximum (x,-x)$
$x^2$ is differentiable and $x-1$ is continuous and differentiable in the given domain.. make the graph of both and check..