Quartic
- To: mathgroup@smc.vnet.net
- Subject: [mg12435] Quartic
- From: Colin L C Fu <es2136@eng.warwick.ac.uk>
- Date: Thu, 14 May 1998 11:15:46 -0400
- Organization: Warwick University
hiya,
I want to solve 3 quartic eqns.
Solve[{expr1, expr2, expr3 == 0}, A]
As it is too long, I was advised to do the folowing:
First, define the list of three expressions that you sent me before.
_______________________________________
In[1]:= expr = ...
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In[2]:= Short[e1 = First[expr], 5]
Out[2]//Short=
4 3 8 4 2 2 4 2 4
p1 (B + p2) q (q + q q2 (a + q2 ) + q2 (b + a q2 + q2 ))
> --------------------------------------------------------------- + <<4>>
4
q2
_______________________________________
_______________________________________
In[3]:= ccoeffs =
CoefficientList[c[1] + c[2] A + c[3] A^2 + c[4] A^3 + c[5] A^4,
A]
Out[3]= {c[1], c[2], c[3], c[4], c[5]}
_______________________________________
_______________________________________
In[4]:= coefflist = CoefficientList[Collect[e1,A],A];
_______________________________________
_______________________________________
In[5]:= sol = Solve[c[1] + c[2] A + c[3] A^2 + c[4] A^3 + c[5] A^4 == 0,
A];
_______________________________________
_______________________________________
In[6]:= InputForm[First[sol]]
Out[6]//InputForm=
{A -> -c[4]/(4*c[5]) - ...
---------------------------------------
and Using this method, i manage to get the first solution of the 1st
expression.
If I want all the four solutions from the first quartic, I just type
In[6]:= InputForm[sol], right?
So I get all the four solutions. However, all the four solutions are
the same in symbolic.
This is not what I got when I just test the quartic by giving each
variable in the quartic a value in which I used NSolve[expr,A].
Why is that? Are all the four symbolic solutions that I got the correct
answers?
Please advise
As I need to know the answer quit urgent, I have to post it to the
newsgroup. However, I am in debt to those that been helping me too. I
really appreciate it.
Regards
Col