how you do graph polynomial functions having 3 as the highest degree or cubic?

I don't really get the question... You're asking about how to draw the function's graphic? Or how to solve the equation? If you need to draw the graphic, yes, the method is pretty much the same, you give a certain value to x, you solve the equation and you get a y value. Then, you connect the points that have the (x,y) coordinates. This is the easy way of drawing a graph and not the most precise. If you know calculus, there is a certain algorithm of drawing a function's graph, that implies calculating its minimum or maximum points and the inflexion points (first and second derivate of the function) and checking weather the graph is ascending or descending between these points... All without giving values to x... But I'm guessing you haven't studied calculus by now.