Mathematics tools

Hi all,
I am newbie at Moodle and I face a problem with the Tex Notation filter. It seems not operate. I run the Tex Filter debugger and the results are:

3rd option: (Show a graphic image of the algebraic expression rendered with mimetex.)
++++++++++++++++++++++
The shell command
"/home/physi/public_html/elearning/filter/tex/mimetex.linux" -e "/home/physi//public_html/elearning/moodledata/filter/tex/d1e56126337cd6e29b16fe759232ce90.gif" --
returned status =
File size of mimetex executable /home/physi/public_html/elearning/filter/tex/mimetex.linux is 491043
The file permissions are: 100777
The md5 checksum of the file is c294ab11905323bb5cb0f451241bedc1
Image not found!

No text output available
+++++++++++++++++++++++

5th option: (Show command execution output from the algebraic expression rendered with Tex/Ghostscript).
+++++++++++++++++++++++

Checking executables

Error: latex executable (/usr/bin/latex) is not readable
Error: dvips executable (/usr/bin/dvips) is not readable
Error: convert executable (/usr/bin/convert) is not readable

base filename for expression is 'd1e56126337cd6e29b16fe759232ce90'

Processing TeX expression:

f(x)=\Bigint_{-\infty}^x~e^{-t^2}dt

$ /usr/bin/latex --interaction=nonstopmode /home/physi//public_html/elearning/moodledata/temp/latex/d1e56126337cd6e29b16fe759232ce90.tex
OUTPUT:
RETURN CODE: 127

$ /usr/bin/dvips -E /home/physi//public_html/elearning/moodledata/temp/latex/d1e56126337cd6e29b16fe759232ce90.dvi -o /home/physi//public_html/elearning/moodledata/temp/latex/d1e56126337cd6e29b16fe759232ce90.ps
OUTPUT:
RETURN CODE: 127

$ /usr/bin/convert -density 240 -trim /home/physi//public_html/elearning/moodledata/temp/latex/d1e56126337cd6e29b16fe759232ce90.ps /home/physi//public_html/elearning/moodledata/temp/latex/d1e56126337cd6e29b16fe759232ce90.gif
OUTPUT:
++++++++++++++++++++++++++
RETURN CODE: 127

Is there any suggestion for this?
Thanks in advance

George