据说著名的数学家高斯,9岁时就能用巧妙的方法速算1+2+3……+100。这种方法叫倒写相加法,现在我们用这种方法来计算1+2+3+……+n。令a=1+2+3+……+n=n+(n-1)+(n-2)+……+1两式相加,得2a=(1+n)+[2+(n-1)]+[3+(n-2)]+……+(n+1)=n(n+1)∴a=12n(n+1)你一定会为高斯这种妙算拍案叫 It is said that the famous mathematician Gauss, at the age of 9 can use the clever way to quickly calculate 1+2+3...+100. This method is called reverse-add. Now we use this method to calculate 1+2+3+...+n. Let a = 1 + 2 + 3 + ... + n = n + (n - 1) + (n - 2) + ... +1 to add two equations to obtain 2a = (1 + n) + [2+ (n -1)]+[3+(n-2)]+......+(n+1)=n(n+1)∴a=12n(n+1) You will surely make a call for Gauss