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Line y = x + k touches x²/9 + y²/4 = 1. Possible k:
A±5
B±√13
C±7
D±√5
Answer & Solution
Correct answer: B. ±√13
Tangency to this ellipse needs k² = a²m² + b² = 9 + 4 = 13 for slope m = 1.
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