4.2.2 Greatest hits from previous weeks

Greatest hits from previous weeks:

4.2.2.1 Matrix in Latex

https://tex.stackexchange.com/questions/204621/matrix-in-latex

I am new to Latex, and I have been trying to get the matrix of following form 
[x11 x12 x13 . . . . x1n 
x21 x22 x23 . . . . x2n 
. 
. 
. 
. 
xd1 xd2 xd3 . . . . xdn] 
...
 

- asked by Lakshmi Narayanan (67 votes), answered by skpblack (107 votes)

4.2.2.2 Underscores in words (text)

https://tex.stackexchange.com/questions/48632/underscores-in-words-text

How can I produce the text Word_one_two in LaTeX? 
I tried: 
Samp\_Dist\_Corr 
But, it doesn't quite look right. Also, I want it in the typewriter font, so actually, I'm doing: 
...
 

- asked by Flux Capacitor (125 votes), answered by David Carlisle (113 votes)