1234+2345+3456+4567+5678+6789怎么用简便方法计算

1234=12342345=1234+11113456=2345+1111=1234+1111×24567=3456+1111=1234+1111×35678=1234+1111×46789=1234+1111×5所以结果=1234×6+1111×(1+2+3+4+5)=24069学过等差数列的话：(1234+6789)*6/2=24069...