Gate 2002 - ME

Question

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) $f(x) = Maximum (x,-x)$

Comments

@Hirak

$x^2$ is differentiable and $x-1$ is continuous and differentiable in the given domain.. make the graph of both and check.. 

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Sorry.. i have went terribly wrong, Thnaks a TON for making it right.. :)

Answer 1

Actually $|x|$=maximum(x,-x) , you can verify this here https://math.stackexchange.com/questions/1856255/prove-x-max-x-x

and we know that $|x|$  is not differentiable at x=0 which is in interval [-1,1] .

Rest of the functions are continuous and differentiable everywhere. 

so option D.