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Problem 15 - Entrance Test

If a and b are the roots of x^2 + 3x + 1 = 0, find a^2 + b^2.

Correct: B

By Vieta's formulas, a + b = -3 and ab = 1. We want to find a^2 + b^2. a^2 + b^2 = (a+b)^2 - 2ab = (-3)^2 - 2(1) = 9 - 2 = 7.