For the following exercises, use the limit definition of derivative to show that the derivative does not exist at x = a for each of the given functions
1. f(x) = x1/3, x = 0
2. f(x) = x23, x = 0
3. f(x) = {1, x<1 X, X1 *=1
4. f(x) = 6 x = 0 47.