There is a stair of 10 steps.IF you can only go up for 1 steps or 2 steps once.How many ways can

分类: 作业答案 • 2022-03-06 18:28:34

问题描述：

There is a stair of 10 steps.IF you can only go up for 1 steps or 2 steps once.How many ways can
you usetogetto the10th step?

答

2+2+2+2+2一种方法2+2+2+2+1+16!/(4!x2!)=15种2+2+2+1+1+1+17!/(3!x4!)=35种2+2+6个18!/(2!x6!)=28种2+8个19!/8!=9种10个1 一种方法一共1+15+35+28+9+1=89种方法...