简便算法.1.9+99+999+9999 2.94=88+90+92+89+93+85+94

问题描述:

简便算法.1.9+99+999+9999 2.94=88+90+92+89+93+85+94

1.9+99+999+9999
=10-1+100-1+1000-1+10000-1
=11110-4
=11106
2.94=88+90+92+89+93+85+94
这个题目不清楚