# L'Hopitals Rule

1. Dec 5, 2006

### kasse

Can one use L'Hopital's Rule on the indeterminate form (-∞)/∞ ?

And by the way, is there a way to write mathematical signs like ∞, the integral sign etc except google-ing, cutting and pasting?

Last edited: Dec 5, 2006
2. Dec 5, 2006

### courtrigrad

I think you can. It would probably be:

$$-\lim_{x\rightarrow c} \frac{f(x)}{g(x)}$$ so that both functions approach $$\infty$$

you write those signs in $$tags as follows: \infty \int Last edited: Dec 5, 2006 3. Dec 5, 2006 ### kasse Yes, it's a french name. But that doesn't really help me a lot :tongue2: 4. Dec 5, 2006 ### kasse OK, thanks! 5. Dec 5, 2006 ### Tomsk I'm not sure, I think its only 0/0, as it comes from the Taylor expansion about the point that x approaches, ie. [tex]\lim_{x\rightarrow a}\frac{f(x)}{g(x)} = \lim_{x\rightarrow a}\frac{f(a) + f'(x)(x-a) + ...}{g(a) + g'(x)(x-a) + ...} = \lim_{x\rightarrow a}\frac{f'(x)}{g'(x)}$$

With f(a)=g(a)=0

Something like that anyway.

6. Dec 5, 2006

### courtrigrad

No you can use L'Hopitals Rule for indeterminate forms, not just 0/0.

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