Math Is Fun Forum

abotaha

Member

Registered: 2010-07-18

Posts: 13

solve system of equations

Hi guys,
this time i have more complicated nonlinear system equations:

It is system of 3 equations:

where A,B,C,D, and E  are constant.

Any suggestion to solve this system.

Last edited by abotaha (2010-08-02 23:15:40)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: solve system of equations

Hi abotaha;

Here are the 2 simplest answers:

There are others.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

abotaha

Member

Registered: 2010-07-18

Posts: 13

Re: solve system of equations

hi bobbym,
thanks foo the help.
you mentioned that there are others solution.
could you please provide me the other, because z=0 is not a good solution in my model.
Moreover, the complex values are also not a good solution. since my model is only for real values.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: solve system of equations

Hi abotaha;

On the other 2, I posted you do not have to worry about them being complex unless A^2 is greater than BE.

Here is another solution:

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

abotaha

Member

Registered: 2010-07-18

Posts: 13

Re: solve system of equations

bobbym

Thanks too much, you are very helpful.

Cheers,

abotaha

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: solve system of equations

Hi abotaha;

Here are 2 more: Just amounting to sign reversals.

This time we got really lucky that there are nice neat solutions. Which by the way you should check of course. Keep in mind that when solving a real world problem rather than a book one that will rarely be the case. Try to formulate your problem so that the non linear terms aren't there to begin with. You do that by making linear assumptions for them. Your answers may be only approximations but at least the math will be doable.

What I am saying is that solving non linear simultaneous equations is very, very difficult.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.