GCDEF gave you the hints that you need to make your program right. Also, please format your code. Use 'Go Advanced' then select the code then press '#' It makes the code much easier to read.

Code:
#include "stdafx.h"
#include <iostream>
#include <cmath>
using namespace std;

int main()
{
double x;

     cout.precision(4);
     cout << " x sqrt(x) x^2\n\n x^3\n";

     for (x = 1.0; x <= 20.0; x++) {
          cout.width();
          cout << x*x*x << " ";
          cout.width(7);
          cout << x << " ";
          cout.width(7);
          cout << sqrt(x) << " ";
          cout.width(7);
          cout << x*x << '\n';
     }
     system("pause");
     return 0;
}
When you have \n in a string this causes a new line to be started in the output. So the \n\n after x^2 causes 2 new lines to be output which is probably not what you want. You also want the output in the same order as your heading which is x sqrt(x) x^2 and x^3 but you are outputting in the order x^3 x sqrt(x) x^2. Cout outputs in the order that it is used.