Step 1: Understanding the Concept:
Geometric mean \(= \sqrt{\alpha\beta} = 6 \implies \alpha\beta = 36\). For quadratic \(2x^2 - 25x + \lambda = 0\), product of roots = \(\lambda/2\). So \(\lambda/2 = 36 \implies \lambda = 72\).
Step 2: Detailed Explanation:
No further steps.
Step 3: Final Answer:
Option (D).