1*3+2*4+3*5+4*6+``````19*21+20*22=
人气:191 ℃ 时间:2019-12-18 23:32:03
解答
1*3+2*4+3*5+4*6+``````19*21+20*22
=4-1 +9-1 +16-1 +...+400-1 +441-1
=1²+2²+3²+...+21² -21
=21*(21+1)*(2*21+1)/6 -21
=3311-21
=3290
推荐
- 1/3+1/(2*4)+1/(3*5)+1/(4+6).+1/(19*21)+1/(20*22)
- 1-2+3-4+5-6+7...+19-20+21怎么计算
- 19.1,20.0,21.2,18.8,19.6,20.5,22.0,21.6,19.4,20.3
- 2^2/1*3+4^2/3*5+6^2/5*7+.+20^2/19*21
- 2^2/(1*3)+4^2/(3*5)+^.+20^2/(19*21)=
- 分段函数分段点处的导数如何求?
- 3(x-y)^2-7(x-y)+8(y-x)^2+6(y-x)合并同类项.
- 按形状分,桥有___.___.___等
猜你喜欢