(√2 − 1/√2)² =

Correct answer: 1/2. √2 − 1/√2 = (2 − 1)/√2 = 1/√2, and (1/√2)² = 1/2.

• 3/2: 3/2 results from an incorrect expansion.
• −1/2: A square cannot be negative, so −1/2 is impossible.
• None of these: “None of these” is incorrect because 1/2 is correct.