1.题意：给一个函数F（X）的表达式，求其最值，自变量定义域为0到100
2.分析：写出题面函数的导函数的表达式，二分求导函数的零点，对应的就是极值点
3.代码：
1 # include <iostream> 2 # include <cstdio> 3 # include <cmath> 4 using namespace std; 5 const double eps=1e-8; 6 double Y; 7 int sgn(double x) 8 { 9 if(fabs(x)<eps) return 0; 10 if(x>0) return 1; 11 else return -1; 12 } 13 double F(double x) 14 { 15 return 6.0*pow(x,7)+8.0*pow(x,6)+7.0*pow(x,3)+5.0*pow(x,2)-Y*x; 16 } 17 double f(double x) 18 { 19 return 42.0*pow(x,6)+48.0*pow(x,5)+21.0*pow(x,2)+10.0*x-Y; 20 } 21 void Solve() 22 { 23 scanf("%lf",&Y); 24 double l=0; 25 double r=100; 26 while(r-l>eps) 27 { 28 double mid=l+(r-l)/2.0; 29 if(sgn(f(mid))>0) r=mid; 30 else l=mid; 31 } 32 printf("%.4f ",F(l)); 33 } 34 int main() 35 { 36 int T; 37 scanf("%d",&T); 38 while(T--) 39 { 40 Solve(); 41 } 42 return 0; 43 }