题目

Manhattan Island is surrounded on the east by the East and Harlem Rivers and on the west by the North and Hudson Rivers.It links with the other four towns which make up New York City and with New Jersey are by means of subways,underground tunnels and bridges which lead into Manhanttan from the surrounding area. The Brooklyn Bridge was the first suspension bridge to link Brooklyn to Manhanttan.It is also the second oldest bridge in New York.The architect was John Augustus Roebling,who was the chief engineer of the suspended Railroad Bridge at Niagara Falls. Misfortune accompanied the building o数轴是一个非常重要的数学工具，它使数和数轴上的点建立起对应关系，揭示了数与点之间的内在联系，它是“数形结合”的基础．在数轴上若点A、B分别表示有理数a、b ，在数轴上A、B两点之间的距离AB=| a-b | ．结合数轴与绝对值的知识回答下列问题：（1）数轴上表示﹣3和2的两点之间的距离是_____；数轴上表示 x 和 -3 两点之间的距离是_____；（2）若a表示一个有理数，则|a+4|+|a﹣2|有最小值吗？若有，请求出最小值；若没有，请说明理由；（3）当a =_____时，|a+4|+|a﹣1|+|a﹣2|的值最小，最小值是_____．