# SAT - difference of cubes?

I was working with a student a couple of weeks ago when we encountered a practice problem that required her to factor a difference of cubes.

I was surprised to see that concept among the practice problems, and a Google search didn't include it among any of the SAT "formulas you must know" or "concepts you must know". Since it isn't as common as the rest of the Algebra II concepts I have seen on the SAT practice, I have to wonder - is it actually likely to be included on the new SAT? I don't see it as something you would derive in under 5 minutes, so the even the above-average student would either have it memorized (and be able to use it) or they wouldn't, and normally the SAT doesn't require that level of simple memorization to solve problems

Does anyone know if it is something that you need to have memorized, or was that a fluke of the Khan Academy practice problems?

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