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Old October 19th, 2008, 08:26 AM
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Default solve equation for x with lnx and x

Hi, is it possible to solve the equation

y = alnx + bx + c?

I made it myself as it seems to best model something, and want a computer program i'm writing to be able to calculate x. Is this actually possible?

Thanks very much in advance for your help,

James
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Old October 19th, 2008, 05:35 PM
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Originally Posted by jsab500 View Post
Hi, is it possible to solve the equation

y = alnx + bx + c?

I made it myself as it seems to best model something, and want a computer program i'm writing to be able to calculate x. Is this actually possible?

Thanks very much in advance for your help,

James
Do you want to solve for x in terms of y?

An exact solution will require using the Lambert W-function.
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Old October 20th, 2008, 03:31 AM
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Yes in terms of y.

How would i go about doing that?

Thanks
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Old October 20th, 2008, 03:57 AM
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Yes in terms of y.

How would i go about doing that?

Thanks
Are you familiar with the Lambert W-function?

What's wrong with using a numerical procedure to get an approximate value of x for a given value of y .....?
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Old October 20th, 2008, 07:14 AM
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nothing's wrong with it, but if there was a way to just get x = whatever, it would be significantly simpler. I'll have a look at that Lambert-W function.

Thanks a lot
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