public MathList reductionDuplicates() {
        for (int i = 0; i < this.size(); i++) {
            MathList sublist = new MathList();
            sublist.addAll(this.subList(i + 1, this.size()));
            for (int j = sublist.size() - 1; j >= 0; j--) {
                if (this.get(i).toString().equals(sublist.get(j).toString())) {
                    this.remove(i + j + 1);

                }
            }

        }
        return this;
    }