(2乘以4)/2+(4乘以6)/2+(6乘以8)/2+……+(98乘以100)/2
问题描述：
(2乘以4)/2+(4乘以6)/2+(6乘以8)/2+……+(98乘以100)/2
答
数列通项an=2n*(2n+2)/2=2n(n+1)=2n^2+2n=2(n^2+n)(2乘以4)/2+(4乘以6)/2+(6乘以8)/2+……+(98乘以100)/2=2[(1^2+1)+(2^2+2)+(3^2+3)+.+(49^2+49)]=2(1^2+2^2+3^2+.+49^2)+2(1+2+3+.+49)已知公式：1^2+2^2+3^2+.+n^2...