What is the time complexity of the Master Theorem's 'Case 1', where the work at the leaves dominates the total cost?

Θ(n^log_b a)

The Master Theorem provides a cookbook method for solving recurrences of the form T(n) = aT(n/b) + f(n). Case 1 occurs when f(n) is polynomially smaller than n^log_b a, meaning the recursive calls at the base of the tree dictate the complexity.