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Re: Using Coefficient on an equation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg95444] Re: [mg95433] Using Coefficient on an equation
  • From: "Scot T. Martin" <smartin at deas.harvard.edu>
  • Date: Mon, 19 Jan 2009 02:54:56 -0500 (EST)
  • References: <200901181033.FAA13999@smc.vnet.net>

Carlos, here may be what you're looking for:

In[1]:= f=a*x^2+b*x+c==0
Out[1]= c+b x+a x^2==0

In[2]:= Coefficient[f,x^2]
Out[2]= 0

In[3]:= Coefficient[f[[1]],x^2]
Out[3]= a



On Sun, 18 Jan 2009, carlos at colorado.edu wrote:

> If f=a*x^2+b*x+c, Coefficient[f,x^2] obviously returns a.
> But if f=a*x^2+b*x+c==0, it returns 0.
>
> The problem arose using the Calculus`VariationalMethods` package.
> It (unfortunately) returns the Euler-Lagrange equations as
> such, so I have to remove the useless ==0 appendage for
> Coefficient to work properly. Is there a simple direct way out?
>
>


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