【導(dǎo)讀】按一定順序排列的一列數(shù)叫數(shù)列。數(shù)列:7,6,5,4。它們不是同一數(shù)列。數(shù)列:1,-1,1,-1,···。這個(gè)常數(shù)叫做等差數(shù)列的公差.如果是請(qǐng)指出公差。當(dāng)d=0時(shí),為常數(shù)列。等差數(shù)列的前m項(xiàng)和,后m項(xiàng)和,再m項(xiàng)和……也構(gòu)成等差數(shù)列。處理《優(yōu)化方案》習(xí)題;