Further Maths - L'Hôpital's Rule


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2021-11-25

What is L’Hôpital’s rule used for?


Finding the limit of two functions divided together.

What is
\[\lim _ {x \to a} \frac{f(x)}{g(x)}\]

equivalent to??

\[\lim_{x \to a} \frac{f'(x)}{g'(x)}\]
What technique could you use for finding the value of
\[\frac{\sin(x)}{x}\]

at $x = 0$?? L’Hôpital’s rule.

What are the conditions for applying L’Hôpital’s rule for
\[\lim _ {x \to a} \frac{f(x)}{g(x)}\]

??

\[\frac{f(x)}{g(x)} = \frac{0}{0}\]

or

\[\frac{f(x)}{g(x)} = \frac{\pm \infty}{\pm \infty}\]

What is

\[\lim _ {x \to a} \frac{f(x)}{g(x)}\]

equivalent to?


\[\lim _ {x \to a} \frac{f'(x)}{g'(x)}\]
How could you evaluate
\[\lim _ {x \to -\infty} x e^x\]

??

\[\lim_{x \to -\infty} \frac{x}{1/e^x}\]

What technique could you use for finding the value of

\[\frac{\sin(x)}{x}\]

at $x = 0$?


L’Hôpital’s rule.

What are the conditions for applying L’Hôpital’s rule for

\[\lim _ {x \to a} \frac{f(x)}{g(x)}\]

?


\[\frac{f(x)}{g(x)} = \frac{0}{0}\]

or

\[\frac{f(x)}{g(x)} = \frac{\pm \infty}{\pm \infty}\]

How could you find the limit of the product of two functions $f(x)g(x)$ when their product is undefined?


\[f(x)g(x) \equiv \frac{g(x)}{1/f(x)} \equiv \frac{f(x)}{1/g(x)}\]

and use L’Hôpital’s rule.

How could you evaluate

\[\lim _ {x \to -\infty} x e^x\]

?


\[\lim _ {x \to -\infty} \frac{x}{1/e^x}\]



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