计算.(99…9)×(99…9)+(199…9) n个9 n个9 n个9

问题描述:

计算.(99…9)×(99…9)+(199…9) n个9 n个9 n个9

(99…9)×(99…9)+(199…9)
=(99…9)×(99…9)+99…9+100...0
=(99…9)×(99…9+1)+100...0
=(99…9)×(100…0)+100...0
=100...0×(99...9+1)
=100...0×100...0
=100...0
2n个0