Hi everyone! I just got out of class and was reviewing my notes. In one of the example exercises, I found a technique that I'm not familiar with. Here's the example question:
The problem that I have is in the final step (this also isn't fully simplified, but I didn't have time to type the whole thing since I just taught myself LaTeX in the past 20 minutes ). Where does the
come from? I heard the word "substitution" mentioned, but that's all I know. An explanation would be greatly appreciated! Also, would it be possible for you to show a minor amount of work to help explain the technique?
Thanks a lot!