Question: Find the value of k for which the function f(x) = kx^2 + 2x + 1 is differentiable at x = 0.
Options:
Correct Answer: 0
Solution:
f\'(x) = 2kx + 2. At x = 0, f\'(0) = 2. The function is differentiable for any k, but k = 0 gives a constant function.