Contact us
Choose a category below so we can get back to you as quickly as possible.
因為k(k+1)=k²;+k所以1*2+2*3+3*4+4*5+5*6+6*7+7*8+8*9+9*10+10*11 ````=1²;+1+2²;+2+3²;+3+4²;+4+5²;+5+6²;+6+7²;+7+8²;+8+9²;+9+10²;+10 ```=1²;+2²;+3…
We and our partners use cookies and other technologies to analyze traffic and optimize your experience. View more info and control your cookies settings at any time in our Cookies Policy.