<p>I have been working my way through the SparkNotes review book and tests as well, and yes, I’ve been finding quite a few mistakes. Sometimes I can figure out what they really meant (for example, they probably meant 4x(x^2-2x-1), which would indeed factor to 4x(x-1)^2), but sometimes they’re just plain wrong. When taking a practice test for Biology yesterday, it literally gave me a message that said “B is not the correct answer. You should have selected B.” I wouldn’t worry about it too much. The principles that they’re teaching are sound even if the examples and problems aren’t necessarily.</p>