Contact us
Choose a category below so we can get back to you as quickly as possible.
1、求項數:[(n-2)-2]/1+1=n-3 2、求和:(2+n-2)*(n-3)/2=n(n-3)/2
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.