integrate and pnz questions



I stumbled upon the following

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myuser at myhost:~$ maxima -b bug1.max
Maxima 5.15.0 http://maxima.sourceforge.net
Using Lisp SBCL 1.0.11.debian
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1)                           batch(bug1.max)

batching /home/myuser/bug1.max
(%i2)                          display2d : false
(%o2) false
(%i3) integrate(x/(1-x),x,-1,1)
Is  zeroa  positive, negative, or zero?
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what does zeroa mean here?

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myuser at myhost:~$ maxima -b bug2.max
Maxima 5.15.0 http://maxima.sourceforge.net
Using Lisp SBCL 1.0.11.debian
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1)                           batch(bug2.max)

batching /home/myuser/bug2.max
(%i2)                          display2d : false
(%o2) false
(%i3) integrate(1/x,x,-1,1)
Is  x-1  positive, negative, or zero?
----------------------------------------------------------

isn't x-1 < 1-1 = 0?
how does this pnz question help here?

Regards Andre