Contact us
Choose a category below so we can get back to you as quickly as possible.
給你推一下吧.設此數列為a,a+d,a+2d,a+3d,…,a+(n-1)d,則前n項的和為 Sn=a+(a+d)+(a+2d)+(a+3d)+…+[a+(n-1)d] =n*a+d[1+2+3+…+(n-1)] =n*a+n*(n-1)*d/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.