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#include <map>
#include <set>
#include <list>
#include <stack>
#include <queue>
#include <vector>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
int t;
scanf("%d\n", &t);
while (t--)
{
double y;
scanf("%lf", &y);
if (y <= 0)
{
printf("0.0000\n");
continue;
}
double l = 0, r = 100, mid;
while(r - l > 1e-6)
{
mid = (l + r) / 2;
double dx = 42.0 * pow(mid, 6) + 48.0 * pow(mid, 5) + 21.0 * pow(mid, 2) + 10.0 * mid;
if (abs(dx - y) < 1e-6)
{
break;
}
else if(dx - y > 1e-6)
{
r = mid;
}
else
{
l = mid;
}
}
if (mid - 100.0 > 1e-6)
{
mid = 100.0;
}
double ans = 6 * pow(mid, 7) + 8 * pow(mid, 6) + 7 * pow(mid, 3) + 5 * pow(mid, 2) - y * mid;
printf("%.4f\n", ans);
}
return 0;
} 原文:http://blog.csdn.net/guard_mine/article/details/40894283