#Finding a limit with l'Hopital

17 messages · Page 1 of 1 (latest)

dusty wadi
#

"Find the limit. Use l'Hopital's rule where appropriate. If there is a more elementary method, try using it. If l'Hopital's rule doesn't apply, explain why."
The limit is lim (as x->∞) of the function (1+ (a/x))^(bx)

I know that for limits of one function divided by another, implementing l'Hopital's rule is pretty simple. I'm not sure where to use it here, however.

unkempt jacinth
#

I can tell you rn it’s 1

#

At least if b>0

#

The denominator grows a lot quicker than the numerator

#

As x gets big

#

Oh shit I misread it as $1+(\frac{a}{x})^{bx}$

raw fieldBOT
#

trigonometric identity

unkempt jacinth
#

Your limit is equal to $\exp(\lim_{x\to \infty}bx\ln(1+\frac{a}{x}))$ a.k.a. $\exp(\lim_{x\to \infty}\frac{\ln(1+\frac{a}{x})}{\frac{1}{bx}})$

raw fieldBOT
#

trigonometric identity

unkempt jacinth
#

Tada you now have a 0/0 form

#

But be careful and make sure to confirm that hopitals rule applies

#

Check that all the limits exist

#

They do btw

unkempt jacinth
unkempt jacinth
#

$e^x=\lim_{n\to \infty}(1+\frac{x}{n})^n$

raw fieldBOT
#

trigonometric identity