by tommywallach Sat Aug 09, 2014 10:19 pm
Hey Baily,
I'm not exactly sure what you mean, but I'll guess you're talking about the method of solving a linear system of two equations known as "elimination" (some people call it "combination," but the name "elimination" is better, because you're trying to eliminate a variable).
The goal is to eliminate a variable. So you'll just do whatever it takes to eliminate the variable.
For example, if you had these equations:
3x + 2y = 15
9x - 2y = 30
What action would eliminate a variable? Obviously, in this case, it would be adding, because 2y + (-2y) = 0.
In another example, if you had this:
5x + 7y = 22
3x + 7y = 30
What action would eliminate the variable here? Obviously, it would be subtraction, because 7y - 7y = 0.
So you just do it based on what will cause the correct result!
-t