等差数列每一项的平方的和是多少
问题描述：
等差数列每一项的平方的和是多少
答
设等差数列第n项为an,公差为d,则an=(n-1)d+a1(an)^2=[(n-1)d+a1]^2(an)^2-(an-1)^2=[(n-1)d+a1]^2-[(n-2)d+a1]^2=(2n-3)d^2+2da1列出前几项(a1)^2=(a1)^2(a2)^2=(a1)^2+d^2+2da1(a3)^2=(a1)^2+4d^2+4da1(a4)^2=(a1)^...