public void TestEx1(double x, double k, double expectedResult, double expectedIterations, double delta = Delta)
        {
            var a = Ex1.F1(x, k);

            if (delta == -1)
            {
                Assert.AreEqual(expectedResult, a[0]);
            }
            else
            {
                Assert.AreEqual(expectedResult, a[0], delta);
            }
            Assert.AreEqual(expectedIterations, a[1]);
        }