limit as x approaches 2 of (sqrt(x+7)-\sqrt[3]{4x+19})/(x-2)

解答

x \to 2 lim (\frac{x + 7 - 3 4 x + 19}{x - 2})

\frac{1}{54}

十进制

0.01851 \dots

求解步骤

x \to 2 lim (\frac{x + 7 - 3 4 x + 19}{x - 2})

使用洛必达法则

= x \to 2 lim \frac{\frac{1}{2 x + 7} - \frac{4}{3 ( 4 x + 19 ) ^{\frac{2}{3}}}}{1}

代入值

x = 2

= \frac{\frac{1}{2 2 + 7} - \frac{4}{3 ( 4 \cdot 2 + 19 ) ^{\frac{2}{3}}}}{1}

化简

\frac{\frac{1}{2 2 + 7} - \frac{4}{3 ( 4 \cdot 2 + 19 ) ^{\frac{2}{3}}}}{1} : \frac{1}{54}

= \frac{1}{54}

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