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isolate variable
05-16-2020, 02:36 PM
Post: #1
isolate variable
Personal:

How to isolate x in equation 1/√x=2*log⁡((y*√x)-0,8), on HP Prime?
I looked in the groups and found no answers.

Grateful

Davidro
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05-16-2020, 03:01 PM (This post was last modified: 05-16-2020 03:11 PM by victorvbc.)
Post: #2
RE: isolate variable
The solution for x in this particular equation can't be expressed in terms of elementary functions. It needs the product logarithm (omega function), which the calc doesn't seem to have, so it won't be able to isolate x, unfortunately.

It can isolate y though:

Code:

solve(1/sqrt(x)=2*ln(sqrt(x)*y-0.8),y)
(e^(1/(2.*√x))+0.8)/√x
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05-16-2020, 03:16 PM
Post: #3
RE: isolate variable
(05-16-2020 03:01 PM)victorvbc Wrote:  The solution for x in this particular equation can't be expressed in terms of elementary functions. It needs the product logarithm (omega function), which the calc doesn't seem to have, so it won't be able to isolate x, unfortunately.

It can isolate y though:

Code:

solve(1/sqrt(x)=2*ln(sqrt(x)*y-0.8),y)
(e^(1/(2.*√x))+0.8)/√x

Ok.,

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05-16-2020, 03:19 PM (This post was last modified: 05-16-2020 03:25 PM by victorvbc.)
Post: #4
RE: isolate variable
Also, you can of course solve numerically (fsolve) for values of y, or graphically using the implicit plot in the advanced graphing app.

   
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05-23-2020, 05:05 PM
Post: #5
RE: isolate variable
(05-16-2020 03:01 PM)victorvbc Wrote:  The solution for x in this particular equation can't be expressed in terms of elementary functions. It needs the product logarithm (omega function), which the calc doesn't seem to have, so it won't be able to isolate x, unfortunately.
X

Lambert W (as an analytic function)
has been missing ever since HP-28C.
– –
VPN
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