The set of all points where the function f(x) = x is differentiable is

(– ∞, ∞) (– ∞, 0) ∪ (0, ∞) (0, ∞) [0, ∞]

(– ∞, ∞)

\(f(x)=\left\{\begin{matrix}x^2&,& x≥0 \\ -x^2&, & x < 0\end{matrix}\right.\) $LHL(0)=RHL(0)=0$ $f'(x)=\left\{\begin{matrix}2x&,& x≥0 \\ -2x&, & x < 0\end{matrix}\right.$ $LHD(0)=RHD(0)=0$ continuous and differentiable for $x∈(– ∞, ∞)$