public void TestAddUnlikeTerms()
        {
            string augend = "X^2";
            string addend = "6";

            string expected = "X^2 + 6";

            MultivariatePolynomial polyAugend = MultivariatePolynomial.Parse(augend);
            MultivariatePolynomial polyAddend = MultivariatePolynomial.Parse(addend);

            MultivariatePolynomial sum = MultivariatePolynomial.Add(polyAugend, polyAddend);
            string actual = sum.ToString();

            TestContext.WriteLine($"Expected: \"{expected}\"; Actual: \"{actual}\"");
            Assert.AreEqual(expected, actual, $"Test of: MultivariatePolynomial.Add({augend}, {addend});");
        }