From the course: Preparing for the GMAT

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Linear equations with two variables

Linear equations with two variables

From the course: Preparing for the GMAT

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Linear equations with two variables

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- [Instructor] So what do we do when we have two equations with two different variables to solve for instead of just one? In this video we'll look at a couple of different ways we can deal with two variable equations. So what if you told me to solve for x in this equation here? I could spend my whole life and never be able to do it, right? Because there's infinite possible values for x, 'cause I don't know what y is. There's no way I can solve for x. However, if you give me a second equation and you said to me okay now tell me what x is. Now I can do it because I have two equations and two variables, so now I can solve. So my preferred way to do this is to stack and add or subtract. So if I stack these things and I look at 'em, I may notice that if I add them these y's will cancel. So if I add x plus x, it's two x, positive y plus negative y is zero, and 10 plus eight is 18. So I'll divide both sides by two, to solve for x is nine. Then all I have to do is plug in nine for x in either…

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