solutions of simple polynomial equations not exact
Subject: solutions of simple polynomial equations not exact
From: Stavros Macrakis
Date: Tue, 28 Nov 2006 12:38:44 -0500
Algsys and Solve act differently in this case:
solve([y^5+y+3],[y]) => return original equation
algsys( <ditto> ) => numerical solutions
This seems confusing, especially since many users use "solve" to
access algsys in general. Compare:
solve([y^5+y+3],[y]) => return original equation
solve([y^5+y+3,x=x],[y,x]) =>
[ [y = - 1.132997481108312, x = %r1],
[y = - 1.1297017250954 %i - 0.47538075666955, x = %r2],
[y = 1.1297017250954 %i - 0.47538075666955, x = %r3],
[y = 1.041879539612078 - 0.82287033810996 %i, x = %r4],
[y = 0.82287033810996 %i + 1.041879539612078, x = %r5] ]
One possible approach here is to have solve *always* try to find all
solutions, including numerical ones -- but we don't currently have a
good rootfinder for non-polynomials (or do we?).
Thoughts?
-s