Question 147008: what is the concept or rules elimination and subtitution
Answer by mangopeeler07(462)   (Show Source):
You can put this solution on YOUR website! what is the concept or rules elimination and subtitution? For elimination, your equations might look like this:  and  . You could easily use elimination there because there is 6x and -6x. By adding these two equations, you can eliminate the x variable and solve for y. So basically, you use elimination when two like terms in two separate expressions add up to zero (meaning they are opposites).
Substitution could either come after the elimination you just did or from the begining. After elimination like the above two equations, you could just plug y back in one of the original equations after you solve for it and then get x. If you do substitution at the beginning, your equations probably give you the value of a variable from the jump, as in and  . Since you have y, then just substitute it into the other equation instead of trying to do elimination there. It's just easier.
For both situations, it is possible to use substitution or elimination and still get the right answer. So there is no set rule that says that you must use either one at a certain time. It's all up to your judgement. Look at the question carefully first, and see which method would be easier to use for each question. That will save you a lot of work, trust me. Good luck!
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