RootFinding: cubic tests now use EvaluatePolynomial

src/UnitTests/RootFindingTests/BrentTest.cs

@@ -69,12 +69,12 @@ namespace MathNet.Numerics.UnitTests.RootFindingTests
         [Test]
         public void Cubic()
         {
-            // with complex roots (looking for the real root only)
-            Func<double, double> f1 = x => 3 * x * x * x + 4 * x * x + 5 * x + 6;
+            // with complex roots (looking for the real root only): 3x^3 + 4x^2 + 5x + 6
+            Func<double, double> f1 = x => Evaluate.Polynomial(x, 6, 5, 4, 3);
             Assert.AreEqual(-1.265328088928, Brent.FindRoot(f1, -2, -1, 1e-8, 100), 1e-6);
 
-            // real roots only
-            Func<double, double> f2 = x => 2 * x * x * x + 4 * x * x - 50 * x + 6;
+            // real roots only: 2x^3 + 4x^2 - 50x + 6
+            Func<double, double> f2 = x => Evaluate.Polynomial(x, 6, -50, 4, 2);
             Assert.AreEqual(-6.1466562197069, Brent.FindRoot(f2, -6.5, -5.5, 1e-8, 100), 1e-6);
             Assert.AreEqual(0.12124737195841, Brent.FindRoot(f2, -0.5, 0.5, 1e-8, 100), 1e-6);
             Assert.AreEqual(4.0254088477485, Brent.FindRoot(f2, 3.5, 4.5, 1e-8, 100), 1e-6);

src/UnitTests/RootFindingTests/NewtonRaphsonTest.cs

@@ -103,15 +103,15 @@ namespace MathNet.Numerics.UnitTests.RootFindingTests
         [Test]
         public void Cubic()
         {
-            // with complex roots (looking for the real root only)
-            Func<double, double> f1 = x => 3*x*x*x + 4*x*x + 5*x + 6;
-            Func<double, double> df1 = x => 9*x*x + 8*x + 5;
+            // with complex roots (looking for the real root only): 3x^3 + 4x^2 + 5x + 6, derivative 9x^2 + 8x + 5
+            Func<double, double> f1 = x => Evaluate.Polynomial(x, 6, 5, 4, 3);
+            Func<double, double> df1 = x => Evaluate.Polynomial(x, 5, 8, 9);
             Assert.AreEqual(-1.265328088928, HybridNewtonRaphson.FindRoot(f1, df1, -2, -1, 1e-10, 100, 20), 1e-6);
             Assert.AreEqual(-1.265328088928, HybridNewtonRaphson.FindRoot(f1, df1, -5, 5, 1e-10, 100, 20), 1e-6);
 
-            // real roots only
-            Func<double, double> f2 = x => 2*x*x*x + 4*x*x - 50*x + 6;
-            Func<double, double> df2 = x => 6*x*x + 8*x - 50;
+            // real roots only: 2x^3 + 4x^2 - 50x + 6, derivative 6x^2 + 8x - 50
+            Func<double, double> f2 = x => Evaluate.Polynomial(x, 6, -50, 4, 2);
+            Func<double, double> df2 = x => Evaluate.Polynomial(x, -50, 8, 6);
             Assert.AreEqual(-6.1466562197069, HybridNewtonRaphson.FindRoot(f2, df2, -8, -5, 1e-10, 100, 20), 1e-6);
             Assert.AreEqual(0.12124737195841, HybridNewtonRaphson.FindRoot(f2, df2, -1, 1, 1e-10, 100, 20), 1e-6);
             Assert.AreEqual(4.0254088477485, HybridNewtonRaphson.FindRoot(f2, df2, 3, 5, 1e-10, 100, 20), 1e-6);