#2333 doesn't factor simple expression

[marek]

expand( (x - 4 + sqrt(7))*(x - 4 - sqrt(7)) );
factor(%);

it gives result
x^2 - 8*x + 9 instead of (x - 4 + sqrt(7))*(x - 4 - sqrt(7))

tested:
1)
Maxima version: 5.20.1
Maxima build date: 8:48 2/16/2010
Host type: i686-pc-linux-gnu
Lisp implementation type: GNU Common Lisp (GCL)
Lisp implementation version: GCL 2.6.7

2)
http://icm.mcs.kent.edu/research/demo.html

[Aleksas]

Do

expand( (x - 4 + sqrt(7))*(x - 4 - sqrt(7)) );
factor(%,a^2-7);
subst(a=sqrt(7),%);

Aleksas D.

[Aleksas]

Demo from
http://icm.mcs.kent.edu/research/demo.html
does not work.
I use windows 7 and firefox.

Do you have instructions for use?