Extraneous equations add parameters. As I said, solve gives solutions that
are correct for *all* values of *all *parameters.
Thus:
solve([x=0],[x]) => [[x=0]]
but
solve([x=0,y=2],[x]) => []
because there is no solution for *all* values of y, which is considered a
parameter, since it is not listed as a variable.
In your example, you have equations like h0 = g0 + f0 - e0 which are
composed entirely of parameters.
-s
On Wed, Jun 12, 2013 at 12:21 PM, Henry Baker <hbaker1 at pipeline.com> wrote:
> Your comment doesn't appear to me to be relevant to the particular set of
> equations that I gave.
>
> The equations are all linear, and solve works fine without the extraneous
> equations:
>
> (%i22) eqn12;
> (%o22) [d0 = c0 + b0, d1 = c1 + b1, d2 = c2 + b2]
> (%i23) d;
> (%o23) [d0, d1, d2]
> (%i24) solve(eqn12,d);
> (%o24) [[d0 = c0 + b0, d1 = c1 + b1, d2 = c2 + b2]]
> (%i25)
>
> How can the extraneous (linear) equations screw up solve?
>
> At 09:08 AM 6/12/2013, Stavros Macrakis wrote:
> >Solve only gives solutions valid for all values of parameters (as opposed
> to variables). For example:
> >
> >(%i12) solve([x=a,x=-a],[x]); <<< no solutions for all a
> >(%o12) []
> >(%i13) solve([x=a,x=-a],[x,a]); <<< make a into a variable
> >(%o13) [[x = 0, a = 0]]
> >
> >On Wed, Jun 12, 2013 at 11:38 AM, Henry Baker <hbaker1 at pipeline.com>
> wrote:
> >Solve doesn't work, either!
> >
> >(%i7) d;
> >(%o7) [d0, d1, d2]
> >(%i8) eqns;
> >(%o8) [d0 = c0 + b0, d1 = c1 + b1, d2 = c2 + b2, h0 = g0 + f0 - e0,
> >h1 = g1 + f1 - e1, h2 = g2 + f2 - e2, f0 = e0 + b0, f1 = e1 + b1,
> >f2 = e2 + b2, g0 = e0 + c0, g1 = e1 + c1, g2 = e2 + c2]
> >(%i9) solve(eqns,d);
> >(%o9) []
> >(%i10)
>
>