4. Sendo \( f(x)=\frac{x^{3}-1}{2 x} \) calcule \( f^{\prime}(-1) \)
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Para calcular a derivada de \( f(x) = \frac{x^{3}-1}{2x} \), podemos usar a regra do quociente. A derivada do quociente \( \frac{u}{v} \) é dada por: \[ f'(x) = \frac{u'v - uv'}{v^2} \] onde \( u = x^3 - 1 \) e \( v = 2x \). Então, encontramos \( u' \) e \( v' \): \[ u' = 3x^2 \quad \text{e} \quad v' = 2 \] Agora, vamos aplicar a fórmula: \[ f'(x) = \frac{(3x^2)(2x) - (x^3 - 1)(2)}{(2x)^2} = \frac{6x^3 - 2(x^3 - 1)}{4x^2} \] Simplificando: \[ f'(x) = \frac{6x^3 - 2x^3 + 2}{4x^2} = \frac{4x^3 + 2}{4x^2} = \frac{4x^3}{4x^2} + \frac{2}{4x^2} = x + \frac{1}{2x^2} \] Agora que temos a expressão para a derivada, vamos calcular \( f'(-1) \): \[ f'(-1) = -1 + \frac{1}{2(-1)^2} = -1 + \frac{1}{2} = -1 + 0.5 = -0.5 \] Portanto, \( f^{\prime}(-1) = -0.5 \).