题目

Ready, Set, Jump!For skydivers, the sky isn't the limit. It's just the beginning. Thousands of people try skydiving each year. Some only jump once, while others go on to experience lifelong adventures, flying and turning over through the air.Skydiving is a method of leaving an airplane and returning to the earth with the help of gravity, then slowing down by using parachute （降落伞）. It may include more or less free-fall, a time during which the parachute has not been used and the body gradually accelerates（加速）to the highest speed.There are three choices for the beginners. Howev求未知数x． 456×x＝56088