26: After substituting the limit point into the given expression you should get

How did we get the last step? When an integer k satisfies k > 0, then the denominator is positive and the conclusion follows. If k < 0, then we again divide by a positive number. What about k = 0? Then in the denominator we have 0⁺⋅(−1) = 0^-, so here the situation is different and the sign changes.

Hint on limit at 1/2 from the left
Hint on limit at 1/2 from the right
Hint on limit at k from the left
Answer