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Let a, b ∈ R be such that the equation ax 2 – 2bx + 15 = 0 has a repeated root α . If α and β are the roots of the equation x 2 – 2bx + 21 = 0, then α 2 + β 2 is equal to

1. 37
2. 58
3. 68
4. 92

Correct answer: 58

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