title: O notation for my algorithm
body: <p>I want to compare three algorithms in case of steps of calculation, but I'm not very familiar with the O notation. The steps of calculation for each algorithm depend on three parameters (x,y,z):<br>
  algorithm 1) number_of_steps = x^2 * y * z - xyz<br>
  algorithm 2) number_of_steps = x^2 * y^2 * z - xyz<br>
  algorithm 3) number_of_steps = x^2 * y^2 * z^2 - xyz<br>
  There is not a huge difference between x, y and z - maybe one of the value is twice or triple another one, but not more.
  How would it look in o notation? There are some solutions I can think about:<br>
  O1(n) vs. O2(n*y) vs. O3(n*y*z)<br>
  or<br>
  O1(n^4) vs. O2(n^5) vs. O3(n^6) - if x, y and z are nearly equal<br>
  or just<br>
  O1(x^2 * y * z) vs. O2(x^2 * y^2 * z) vs. O3(x^2 * y^2 * z^2)<br>
  Which is correct?</p>