高中数学 22 等差数列素材 新人教版必修5 素材.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,1,2,3,4,5,6,7,8,9,10,1,2,3,4,5,6,7,8,9,10,0,等差数列的图象,1,2,3,4,5,6,7,8,9,10,-9,-8,-7,-6,-5,-4,-3,-2,-1,0,-10,等差数列的图象,等差数列前,n,项和,S,n,=,=,.,S,n,=a,1,+a,2,+a,3,+,+a,n-2,+a,n-1,+a,n,(1),S,n,=a,n,+a,n-1,+a,n-2,+,+a,3,+a,2,+a,1,(2),(1)+(2)得,2S,n,=n(a,1,+a,n,),a,1,a,n,