Simply Googling each term above, and searching for the proprietors' sites (first two cases) will get you to websites where you can download extensive user manuals and/or locate very helpful and free tutorials. Look for links including "mathworks" (Matlab) and "wolfram" (Mathematica) in the URL, if you want material published by the proprietors. See also Introduction to Matlab.
In the case of GNU Octave, you'll find a link to support, where you can download an $800$-page reference manual, which I've included here to facilitate your access.
Simply Googling each term above, and searching for the proprietors' sites (first two cases) will get you to websites where you can download extensive user manuals and/or locate very helpful and free tutorials. Look for links including "mathworks" (Matlab) and "wolfram" (Mathematica) in the URL, if you want material published by the proprietors. See also Introduction to Matlab.
In the case of GNU Octave, you'll find a link to support, where you can download an $800$-page reference manual, which I've included here to facilitate your access.
For $\LaTeX$, you might want to check out the website latex.project.org/guides website where you'll find resources (free) under the heading "Documentation". I'll include a link to The (Not so) Short Introduction to LaTeX2e (pdf) to facilitate your access.