hdoj1077 The area

#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
    int T;
    double x1, x2, x3, y1, y2, y3, a, b, c, ans;
    scanf("%d", &T);
    while (T--) {
    scanf("%lf%lf%lf%lf%lf%lf", &x1, &y1, &x2, &y2, &x3, &y3);
    a = (y3 - y1) / ((x3 - x1) * (x3 - x1));
    b = -2 * a * x1;
    c = y1 + (b * b) / (4 * a);
    double d = (y2 + y3) * (x3 - x2) / 2;
    ans =
        a / 3 * (x3 * x3 * x3 - x2 * x2 * x2) + b / 2 * (x3 * x3 -
                                 x2 * x2) +
        c * (x3 - x2) - d;
    if (ans < 0)
        ans *= -1;
    printf("%.2lf\n", ans);
    }
}