Verified answer

using System;

using static System.Console;

class Program

{

static void Main() {

double f,x;

Write("x=");

x=double.Parse(ReadLine());

if (x<8)

f=1/(x*x*x*x-6);

else

f=-x*x+x-9;

WriteLine("F(x)="+f.ToString());

}

}