3.等差數(shù)列通項(xiàng)的設(shè)法(1)通項(xiàng)法:設(shè)數(shù)列的通項(xiàng)公式,即設(shè)an=a1+(n-1)d(2)對(duì)稱項(xiàng)設(shè)法:當(dāng)?shù)炔顢?shù)列{an}的項(xiàng)數(shù)為奇數(shù)時(shí),可設(shè)中間一項(xiàng)為a,再以公差為d向兩邊分別設(shè)項(xiàng)為:,a-2d,a-d,a,a+d,a+2d,點(diǎn)擊下載全部:高二數(shù)學(xué)