How to solve this system?
07-06-2017, 01:24 PM
Post: #1
 COB160 Junior Member Posts: 35 Joined: Jul 2017
How to solve this system?
Hi,
Could you tell me how to solve system like this with Hp prime?
https://www.dropbox.com/s/tp4fyfa1c6i8o8...8.png?dl=0

I want the output to be m1<r<m2
thanks
07-06-2017, 06:23 PM
Post: #2
 Han Senior Member Posts: 1,882 Joined: Dec 2013
RE: How to solve this system?
(07-06-2017 01:24 PM)COB160 Wrote:  Hi,
Could you tell me how to solve system like this with Hp prime?
https://www.dropbox.com/s/tp4fyfa1c6i8o8...8.png?dl=0

I want the output to be m1<r<m2
thanks

You need to at least explain which parameters are variables, which are constants, etc. Otherwise, it is not clear what you are trying to solve for.

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07-06-2017, 06:46 PM
Post: #3
 COB160 Junior Member Posts: 35 Joined: Jul 2017
RE: How to solve this system?
Good! How can I do this? Thank u for response
07-06-2017, 08:02 PM
Post: #4
 Han Senior Member Posts: 1,882 Joined: Dec 2013
RE: How to solve this system?
(07-06-2017 06:46 PM)COB160 Wrote:  Good! How can I do this? Thank u for response

No calculator or software of any kind is going to be able to magically determine what parameters are variables (to be solved for) and what parameters are constants. And no one can help you until you at least tell us what it is you want to solve for (r? m1? m2? p1? or p2? ... which?)

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07-06-2017, 08:32 PM
Post: #5
 COB160 Junior Member Posts: 35 Joined: Jul 2017
RE: How to solve this system?
Ok, I'm Solving for p_1>0 and p_2>0
07-06-2017, 10:19 PM (This post was last modified: 07-06-2017 10:39 PM by Helge Gabert.)
Post: #6
 Helge Gabert Senior Member Posts: 467 Joined: Dec 2013
RE: How to solve this system?
Where is the problem?

If m1, m2, r not equal zero, just take the inverse and multiply out.

p1=(-m2+r)/(m1*r+m1-m2*r-m2)
p2=(m1-r)/(denom. as above)

and observe r>m2 and m1>r (which is NOT what you wanted, but you can check various combinations of negative numerator divided by negative denominator and see if find combinations which satisfy m1<r<m2).
07-06-2017, 10:41 PM (This post was last modified: 07-06-2017 10:42 PM by Han.)
Post: #7
 Han Senior Member Posts: 1,882 Joined: Dec 2013
RE: How to solve this system?
As Helge mentioned, this one can be done simply (since you are solving for $$p_1$$ and $$p_2$$ ). On the HP Prime (make sure you are in the CAS view), just type in the right hand side like you see it and press Enter. Then use the simplify key:

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07-06-2017, 11:06 PM
Post: #8
 COB160 Junior Member Posts: 35 Joined: Jul 2017
RE: How to solve this system?
(07-06-2017 10:19 PM)Helge Gabert Wrote:  Where is the problem?

If m1, m2, r not equal zero, just take the inverse and multiply out.

p1=(-m2+r)/(m1*r+m1-m2*r-m2)
p2=(m1-r)/(denom. as above)

and observe r>m2 and m1>r (which is NOT what you wanted, but you can check various combinations of negative numerator divided by negative denominator and see if find combinations which satisfy m1<r<m2).

That is exactly my problem! Can I directly get the result I am searching for? Maybe by using solve function with assumptions on parameters (assumptions that I actually am not able to do...)
07-06-2017, 11:23 PM
Post: #9
 COB160 Junior Member Posts: 35 Joined: Jul 2017
RE: How to solve this system?
(07-06-2017 10:41 PM)Han Wrote:  As Helge mentioned, this one can be done simply (since you are solving for $$p_1$$ and $$p_2$$ ). On the HP Prime (make sure you are in the CAS view), just type in the right hand side like you see it and press Enter. Then use the simplify key:

I get the same result! But by putting this two outcome >0, it outputs m_1>r>m_2, instead of m_2>r>m_1. I think I should make assumption on parameters (using solve function?) in order to get the second solution; am I wrong?
07-07-2017, 12:42 AM
Post: #10
 Han Senior Member Posts: 1,882 Joined: Dec 2013
RE: How to solve this system?
Just factor a -1 from both numerator and denominator.

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07-08-2017, 10:03 AM
Post: #11
 COB160 Junior Member Posts: 35 Joined: Jul 2017
RE: How to solve this system?
(07-07-2017 12:42 AM)Han Wrote:  Just factor a -1 from both numerator and denominator.

Fine, if I type "assume(m1<m2)" and "assume(p1>0 AND p1<1)" and "assume(p2>0 AND p2<1)" (wich are restrictions I intend to impose on this variables), using solve function, can I get directly the m1<r<m2 result?
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