Calculus

[gillgill]

For what values of x is │x^2-4│ not differentiable?
Is there a way to solve it without looking at the graph?

[Hurkyl]

Yep. Differentiate it and see where the derivative doesn't exist.

[quasar987]

You have to use the definition of the derivative (the limit).

Notice how limit from the right and limit from the left are different as x approaches -2 and +2 from both sides.