=1²+2²+3²+.+n²=n(n+1)(2n+1)/6由于1²+2²+3²+.+(2n)²=2n(2n+1)(4n+1)/6=n(2n+1)(4n+1)/3所以n(2n+1)(4n+1)/3=S+2n(n+1)(2n+1)/3S=n(2n+1)(4n+1)/3-2n(n+1)(2n+1)/3=n[(2n+1...