## #1283 Equations scaled incorrectly

closed
nobody
5
2007-10-20
2007-10-19
Anonymous
No

Now, this could be me, but I think that Maxima is not meant to actually change your expression when you ask it to factor it.

I think this session best describes the problem:

(%i48) (10*y-11*%i+2)*(10*z+11*%i+2);
(%o48) (10*y-11*%i+2)*(10*z+11*%i+2)

(%i49) factor(%);
(%o49) (10*y-11*%i+2)*(10*z+11*%i+2)

(%i50) expand(%);
(%o50) 100*y*z-110*%i*z+20*z+110*%i*y+20*y+125

(%i51) factor(%);
(%o51) 5*(10*y-11*%i+2)*(10*z+11*%i+2)

(%i52) expand(%);
(%o52) 500*y*z-550*%i*z+100*z+550*%i*y+100*y+625

(%i53) factor(%);
(%o53) 25*(10*y-11*%i+2)*(10*z+11*%i+2)

(%i54) expand(%);
(%o54) 2500*y*z-2750*%i*z+500*z+2750*%i*y+500*y+3125

(%i55) factor(%);
(%o55) 125*(10*y-11*%i+2)*(10*z+11*%i+2)

(%i56) expand(%);
(%o56) 12500*y*z-13750*%i*z+2500*z+13750*%i*y+2500*y+15625

(%i57) factor(%);
(%o57) 625*(10*y-11*%i+2)*(10*z+11*%i+2)

(%i58) expand(%);
(%o58) 62500*y*z-68750*%i*z+12500*z+68750*%i*y+12500*y+78125

Maxima version: 5.10.0
Maxima build date: 14:57 10/18/2006
host type: i686-pc-linux-gnu
lisp-implementation-type: GNU Common Lisp (GCL)
lisp-implementation-version: GCL 2.6.7

## Discussion

• Viktor Toth - 2007-10-20
• status: open --> closed

• Viktor Toth - 2007-10-20

Logged In: YES
user_id=1023504
Originator: NO

This problem is not reproducible in the current production version. I recommend that you download and use version 5.13.0:

Maxima 5.13.0 http://maxima.sourceforge.net
Using Lisp CLISP 2.35 (2005-08-29)
Dedicated to the memory of William Schelter.
This is a development version of Maxima. The function bug_report()
provides bug reporting information.
(%i1) (10*y-11*%i+2)*(10*z+11*%i+2);
(%o1) (10 y - 11 %i + 2) (10 z + 11 %i + 2)
(%i2) factor(%);
(%o2) (10 y - 11 %i + 2) (10 z + 11 %i + 2)
(%i3) expand(%);
(%o3) 100 y z - 110 %i z + 20 z + 110 %i y + 20 y + 125
(%i4) factor(%);
(%o4) 5 (20 y z - 22 %i z + 4 z + 22 %i y + 4 y + 25)
(%i5) expand(%);
(%o5) 100 y z - 110 %i z + 20 z + 110 %i y + 20 y + 125
(%i6)

Viktor