2+22+222+2222+22222+-------+2222222222請用簡便方法計算
2+22+222+2222+22222+-------+2222222222
=2(1+11+111+…+111111111+1111111111)
=2(123456789+1111111111)
=2*1234567900
=2469135800
找規律:(2)7 8 10()22 38
14
找規律填數7,8,10,填數,22,38
7,8,10,14,22,38