//TODO: explain this eval method
        public double eval(double at) {
            double val = 0;
            for (double coefficient : coefficients) {
                val = val * at + coefficient;
            }
            return val;
        }

        public double eval1(double at) {
            double val = 0;
            for (int i=0; i<coefficients.length; i++) {
                val += coefficients[i] * Math.pow(at, i);
            }
            return val;
        }