$ \underbrace {222…22}_{2000个2}×\underbrace {999…99}_{2000个9}$
$=\underbrace {222…22}_{2000个2}×(1\underbrace {000…00}_{2000个0}-1)$
$=\underbrace {222…22}_{2000个2}×1\underbrace {000…00}_{2000个0}-\underbrace {222…22}_{2000个2}$
$=\underbrace {222…22}_{1999个2}21\underbrace {777…78}_{1999个7}$