题目

  Horseback riding has been popular for centuries for many reasons. Very early in history, horseback riding became a primary means of travel. In the very beginning, horses were used for fighting and hunting. Today, horseback riding is mostly used for fun and therapy (治疗). When choosing a horseback riding camp, you must first decide which style of riding you want to learn. American riding is generally related to cowboys (牛仔) and all kinds of competitions. American saddles(马鞍)were made to make sure that the rider feels comfortable and safe.      English riding, on the 已知 a＞0，解关于x的不等式（x-3）[（a-1）x+3]＞0．