is gelijk aan
|
A. 1 |
B. \(\frac12\) |
C. \(\frac13\) |
D. \(\frac14\) |
E. \(\frac1{12}\) |
[ 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
\(\displaystyle\lim_{x\to8}\frac{\sqrt[3]{x}-2}{x-8}=\;\lim_{x\to8}\frac{x^\frac{1}{3}-2}{x-8}\left(=\frac{0}{0}\right)\buildrel H\over=\;\displaystyle\lim_{x\to8}\frac{\frac{1}{3}x^{-\frac{2}{3}}}{1}\\=\frac{1}{3}8^{-\frac{2}{3}}=\;\frac{1}{3}(2^3)^{-\frac{2}{3}}=\frac{1}{3}2^{-2}=\frac{1}{3}.\frac{1}{4}=\;\;\ldots\)