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Given x^2 - x - 1 = 0 with roots a, b, evaluate the cube sum a^3 + b^3.
A4
B3
C1
D-2
Answer & Solution
Correct answer: A. 4
With a + b = 1 and ab = -1, a^3 + b^3 = (a + b)^3 - 3ab(a + b) = 1 + 3 = 4.
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