...的三位数,且满足各位数字从左向右依次成等差数列。答:从0,1,2,3,4,5,6,7,8,9中任取三个数,组成没有重复数字的三位数,且满足各位数字从左向右依次成等差数列。则这样的三位数有8+6+4+2=20个
高中数学:排列组合答:解:从这10个数码中任取3个,组成一3位数,使数字成等差数列,可按公差的大小分类讨论。即穷举法。(1)公差为1时,123,234,345,456,567,678,789,计7个。(2)公差为-1时,987,876,765,654,543,432,321,210。计8个。(3)公差为2时,135,246,357,468,579,计5个。(4)公差为-2...