等差数列的基本性质⑴公差为d的等差数列,各项同加一数所得数列仍是等差数列,其公差仍为d．⑵公差为d的等差数列,各项同乘以常数k所得数列仍是等差数列,其公差为kd．⑶若{ a }、{ b }为等差数列,则{ a ±b }与{ka ＋b}...