I haven't examined the rest of the code, but I'd write that line like this or

1.     for(int i = -b / (2 * a) - 2; i < -b / (2 * a) + 2; i++)

depending on where you want the a

In

1.     for(i = (-(b)/2(a))-2; i < (-(b)/2(a))+2; i++){
2.       float[] points;
3.       points.add(i);
4.     }    
5.   }

line 24 has no i variable, perhaps you meant the line 23.
Avoid making global variables like i, it is better to declare it locally, inside the loop as allonestring shown.
The line 3 above is strange. Are you aware that when you declare locally a variable here, it is not available outside of the loop?
And there is no add method for an array. Perhaps you want to use an array list.

A whole expressing being tested all the time as a break loop condition?