问题如图所示，求解答，想的头要秃辽

Question

Answer 1

你题目的解答代码如下：

#include<stdio.h>

double f(int n)
{
    int i;
    double s = 0;
    for (i = 2; i <= 2*n; i+=2)
    {
        s += ((i-1) * (i+1)) / (double)i;
    }

    return s;
}

int main()
{
    int n;
    scanf("%d", &n);
    printf("%lf\n", f(n));
    return 0;
}

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