is gelijk aan
A.   1
B.   \(\frac12\)
C.   \(\frac13\)
D.   \(\frac14\)
E.   \(\frac1{12}\)
A    B    C    D    E

[ 5-7151 - op net sinds 17.12.12-(E)-7.11.2024 ]

Translation in   E N G L I S H


is equal to
A.   1
B.   \(\frac12\)
C.   \(\frac13\)
D.   \(\frac14\)
E.   \(\frac1{12}\)

Oplossing - Solution

1ste manier : zonder de regel van de l'Hospital
      wel rekening houdend met (A − B)(A² + AB + B²) = A³ − B³

\(\displaystyle\lim_{x\to8}\frac{\sqrt[3]{x}-2}{x-8}=\displaystyle\lim_{x\to8}\frac{\left(\sqrt[3]{x}-2\right)\left(\sqrt[3]{x^2}+2\sqrt[3]{x}+4\right)}{\left(x-8\right)\left(\sqrt[3]{x^2}+2\sqrt[3]{x}+4\right)}\\=\displaystyle\lim_{x\to8}\frac{x-8}{\left(x-8\right)\left(\sqrt[3]{x^2}+2\sqrt[3]{x}+4\right)}\\=\lim_{x\to8}\frac{1}{\left(\sqrt[3]{x^2}+2\sqrt[3]{x}+4\right)}=\frac{1}{2^2+2.2+4}=\ldots" \)
2de manier : met de regel van de l'Hospital
\(\displaystyle\lim_{x\to8}\frac{\sqrt[3]{x}-2}{x-8}=\;\lim_{x\to8}\frac{x^\frac{1}{3}-2}{x-8}\left(=\frac{0}{0}\right)\buildrel H\over=\;\displaystyle\lim_{x\to8}\frac{\frac{1}{3}x^{-\frac{2}{3}}}{1}\\=\frac{1}{3}8^{-\frac{2}{3}}=\;\frac{1}{3}(2^3)^{-\frac{2}{3}}=\frac{1}{3}2^{-2}=\frac{1}{3}.\frac{1}{4}=\;\;\ldots\)