You can't divide a variable out unless you're sure it's not 0.
i.e. it’s an illegal operation if the variable can possibly equal zero. Conversely, if you know FOR SURE that y is not zero, then you can divide by y.
"StudyBlue is great for studying. I love the study guides, flashcards and quizzes. So extremely helpful for all of my classes!"Alice , Arizona State University
"I'm a student using StudyBlue, and I can 100% say that it helps me so much. Study materials for almost every subject in school are available in StudyBlue. It is so helpful for my education!"Tim , University of Florida
"StudyBlue provides way more features than other studying apps, and thus allows me to learn very quickly!Â I actually feel much more comfortable taking my exams after I study with this app. It's amazing!"Jennifer , Rutgers University
"I love flashcards but carrying around physical flashcards is cumbersome and simply outdated. StudyBlue is exactly what I was looking for!"Justin , LSU