简便递等式计算
1.01×9.9
=（1+0.01）x9.9
=1x9.9+0.01x9.9
=9.9+0.099
=9.999 简便递等式计算
1.01×9.9
=（1+0.01）x9.9
=1x9.9+0.01x9.9
=9.9+0.099
=9.999