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2014-02-15T14:24:20-02:00
Usa a fórmula do X do vértice: \boxed{Xv= \frac{-b}{2.a}}

Xv= \frac{-b}{2.a} \\\\Xv= \frac{-12}{2.(-2)} \\\\Xv= \frac{-12}{-4} \\\\\boxed{Xv=3}

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