- #1

gayani

- 2

- 0

## Homework Statement

Find A so that lim (x+A/x-2A)^x =5

x-> 00

## Homework Equations

## The Attempt at a Solution

got to use lopihtals rule.

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter gayani
- Start date

- #1

gayani

- 2

- 0

Find A so that lim (x+A/x-2A)^x =5

x-> 00

got to use lopihtals rule.

- #2

tiny-tim

Science Advisor

Homework Helper

- 25,838

- 256

Hi gayani! Welcome to PF!

(have an infinity: ∞ and try using the X

Find A so that lim (x+A/x-2A)^x =5

x-> 00

…

got to use lopihtals rule.

hmm … I can't see how to use

but if you write the LHS as (1 + 3A/(x - 2A))

- #3

Mark44

Mentor

- 36,705

- 8,695

Just in case you don't follow what Tiny-tim did, here it is.

You wrote the rational expression as x + A/x - 2A. What I'm pretty sure you meant (and the way Tiny-tim interpreted it) was (x + A)/(x - 2A). What you wrote would be correctly interpreted as the sum and difference of three expressions-- x, A/x, and 2/A, not the quotient of x + A and x - 2A.

What Tiny-tim did was divide x + A by x - 2A, so that (x + A)/(x - 2A) = 1 + 3A/(x - 2A).

- #4

Bohrok

- 867

- 0

Take the natural log of both sides and then take the limit of the natual log of the left side

[tex]\lim_{x\rightarrow\infty} ln\left(1 + \frac{3A} {x-2A}\right)^x= ln (5)[/tex]

You'll have to do some rearranging in order to use l'Hôpital's rule and "solve" for A.

[tex]\lim_{x\rightarrow\infty} ln\left(1 + \frac{3A} {x-2A}\right)^x= ln (5)[/tex]

You'll have to do some rearranging in order to use l'Hôpital's rule and "solve" for A.

Last edited:

Share:

- Last Post

- Replies
- 14

- Views
- 614

- Last Post

- Replies
- 5

- Views
- 413

- Replies
- 0

- Views
- 106

- Last Post

- Replies
- 1

- Views
- 324

- Last Post

- Replies
- 6

- Views
- 374

- Last Post

- Replies
- 5

- Views
- 426

- Last Post

- Replies
- 7

- Views
- 931

- Last Post

- Replies
- 20

- Views
- 623

- Last Post

- Replies
- 3

- Views
- 452

- Last Post

- Replies
- 7

- Views
- 430