Difficulty: Medium
Correct Answer: 34
Explanation:
Introduction / Context:
This problem combines rationalizing a radical fraction and manipulating sums/differences of two variables. The key is to simplify x first, then exploit the given difference x − y to identify y and compute x^2 + y^2 efficiently.
Given Data / Assumptions:
Concept / Approach:
Rationalize x by multiplying numerator and denominator by the conjugate (√2 + 1). Then, given the numerical value of x, use x − y = 4√2 to obtain y. Finally, compute x^2 + y^2 by squaring and adding; conjugate-like structures will cancel mixed terms.
Step-by-Step Solution:
Verification / Alternative check:
Observe that y = 3 − 2√2 satisfies x − y = 4√2 directly; the conjugate structure guarantees mixed terms cancel when squaring and adding.
Why Other Options Are Wrong:
38, 32, 30, and 28 are typical miscomputations from squaring or handling radicals improperly; only 34 is consistent.
Common Pitfalls:
Not rationalizing correctly, or attempting to compute y via a guess without ensuring the exact difference equals 4√2.
Final Answer:
34
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