I already had Algebra 2, second edition, but when I started it I was miffed to find out that the little subscripts that indicate which lesson a problem comes from was missing. Apparently, this was added in the third edition. I didn’t want to buy the entire set from scratch, but that was useful enough to me that I was considering it.

While looking into it, I ran across something that indicated that the third edition is the same as the second edition with that sole difference (the lessons are indicated on each problem in a small font). After finding a good copy on Amazon for $25 shipped, ~~I can confirm that that *is* true for each problem~~, at least through 5 lessons and a quick perusal through the book. But during the fifth problem set I did notice another small difference: The third edition doesn’t have formulas on the back inside cover of the book! There’s a question in lesson 5 that basically requires the formula for the surface area of a sphere (4(pi)r^2). I flipped to the back and bam, a blank page. Not having it in the back was actually helpful in the instance because I actually paused and recalled how they said to remember that formula in Algebra 1 (a picture of the area of 4 circles). But yeah, it was surprising!

Checking the second edition just now, though, they actually don’t have that particular formula! Ha! But I’m right, there is a selection of geometric formulas there in Algebra 2 second edition and it’s not there in Algebra 2 Third Edition.

Now you know.

**Edited to add:** I can definitely confirm that they are NOT identical. Problem set 12, question 24 is almost the same except that an ‘a^2’ is replaced with ‘2^2’ in the problem. This makes the answer completely different, so at least for one problem you cannot trust the 2nd edition answer key for the 3rd edition book. Bummer.