The problem valley is explained (it will be updated year by year). This is the 20 13 version of 5-year senior high school entrance examination and 3-year simulation mathematics. The answer is explained by video, but almost 40% of it is not completely recorded (if there is no explanation, you can copy the content to Baidu, so it won't take too much time, 80% of it can be found, unless it is a square complex calculation, 65%). )