public boolean equals(Object obj) {
    	if(obj != null && obj instanceof Line) {
    		Line line = (Line) obj;
    		if(isEqual(slope, line.slope) && isEqual(intercept, line.intercept) 
    				&& verticalLine == line.verticalLine) {
    			return true;
    		}
    	}
    	return false;
    }