⑴公差為d的等差數(shù)列,各項(xiàng)同加一數(shù)所得數(shù)列仍是等差數(shù)列,其公差仍為d. ⑵公差為d的等差數(shù)列,各項(xiàng)同乘以常數(shù)k所得數(shù)列仍是等差數(shù)列,其公差為kd. ⑶若{ a }、{ b }為等差數(shù)列,則{ a ±b }與{ka +b}(k、b為非零常數(shù))也是等差數(shù)列. ⑷對(duì)任何m、n ,在等差數(shù)列{ a }中有：a = a + (n-m)d,特別地,當(dāng)m = 1時(shí),便得等差數(shù)列的通項(xiàng)公式...