Buy this, only the 2009 edition. . It is also the best math course I have ever seen. . . It's also cheap. 10 soon, hardcover version. . . . I haven't figured out why there is only 2009. . . This book is cheap, but it also has a good use. . . Otherwise, this book can't be played on both sides. . . In addition, I took the math entrance examination 139.