PSAT #2, Section 3, #17

There are a lot of words in this one, but all you’re really being asked to do is FOIL and then substitute. Here’s the FOIL part:


From there, the only given information you need to use is that adbc. Because that’s true, the xy coefficient simplifies to zero! Since you’re only asked for the value of that coefficient, grid in zero and move on.


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