From the course: Preparing for the GMAT

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Quadratic identities

Quadratic identities

From the course: Preparing for the GMAT

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Quadratic identities

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- [Instructor] So certain quadratic equations, i.e. equations with one term being squared are really predictable in terms of how their factors look. So in this video we'll talk about three common quadratic identities so you can more easily recognize them when they popup in GMAT questions. So the first thing I want to do is what's commonly known as the difference of two squares. So what if I had this and I was like hey, factor that. X squared minus y squared. Well this predictably factors into x plus y times x minus y. So, if you saw this side you would know it multiplies into that and if you saw this side you would know it factors into that, so that's one of 'em. What about if we had x minus y squared? Well this is going to turn into if we FOIL it, let's just do that for illustration. X minus y times x minus y. If we do that math x squared minus xy minus another xy plus y squared and I'll simplify that to x squared minus two xy plus y squared. So we want to remember that that is the…

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