I have to concur -- it should be a 2x in there. Having published a handful of math books, I must say it is not unreasonable to assume it is a misprint. They happen relatively often in math publishing, because the vast majority of book proofreaders don't understand math at all, which is kind of sad.
Hey there, just stumbled across your forum. I run the web site www.calculus-help.com and am happy to post a solution. Just follow this link:
Do note that you shouldn't leave y in your answer; instead substitute y = 2x^(2x) back in for it at the end
I just went ahead and registered after I posted the above solution, so you can direct comments and questions to me at this username.