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Factor[] and real numbers???

• To: mathgroup at smc.vnet.net
• Subject: [mg8785] Factor[] and real numbers???
• From: sbecuwe at uia.ua.ac.be (Stefan.Becuwe)
• Date: Thu, 25 Sep 1997 12:26:19 -0400
• Sender: owner-wri-mathgroup at wolfram.com

Hi

According to the Mathematica Book, 
"Factor works only with exact Integer or Rational coefficients, not
 with Real numbers."
 
Knowing this, can anyone explain the following (strange?) results?
(I'm using Mathematica 2.2)
 
 
In[2]:= Factor[Pi x - Pi x^2]

Out[2]= Pi (1 - x) x

In[3]:= Factor[N[3/7,20] x - N[6/7,20]x^2]

Out[3]= 0.85714285714285714286 (0.5 - x) x

In[4]:= Factor[N[3/7,20] x - N[6/7,30]x^2]

Out[4]= 0.857142857142857142857142857143 (0.5 - x) x



Regards

Stefan Becuwe