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At which values of x does the curve y = x³ - 3x have a horizontal tangent?
Ax = ±1
Bx = 0
Cx = ±3
Dx = 1 only
Answer & Solution
Correct answer: A. x = ±1
A horizontal tangent needs 3x² - 3 = 0, so x² = 1 and x = ±1.
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