Question

从1加到100等于5050,用等差数列怎么算?

Answer 1

{an} 是等差数列 n = 1,2,.,a(n+1)-an=d

等差数列{an},Sn= a1+a2+...+an=(a1+an)*n/2

1+2+...+100 = (1+100)*100/2 = 5050