feat: fix test cases

Author: sailok.chinta

src/main/java/com/thealgorithms/maths/QuadraticEquationSolver.java

@@ -1,5 +1,7 @@
 package com.thealgorithms.maths;
 
+import java.util.Arrays;
+
 class ComplexNumber {
     Double real;
     Double imaginary;
@@ -48,7 +50,7 @@ public ComplexNumber[] solveEquation(double a, double b, double c) {
             double realPart = -b / (2 * a);
             double imaginaryPart = Math.sqrt(-discriminant) / (2 * a);
 
-            return new ComplexNumber[] {new ComplexNumber(realPart, imaginaryPart), new ComplexNumber(realPart, imaginaryPart)};
+            return new ComplexNumber[] {new ComplexNumber(realPart, imaginaryPart), new ComplexNumber(realPart, -imaginaryPart)};
         }
 
         // return no roots

src/test/java/com/thealgorithms/maths/QuadraticEquationSolverTest.java

@@ -15,8 +15,10 @@ public void testSolveEquation_realRoots() {
 
         ComplexNumber[] roots = quadraticEquationSolver.solveEquation(a, b, c);
         Assertions.assertEquals(roots.length, 2);
-        Assertions.assertEquals(roots[0].real, -1.6266572504051);
-        Assertions.assertEquals(roots[1].real, -0.27810465435684306);
+        Assertions.assertEquals(roots[0].real, -0.27810465435684306);
+        Assertions.assertNull(roots[0].imaginary);
+        Assertions.assertEquals(roots[1].real, -1.6266572504050616);
+        Assertions.assertNull(roots[1].imaginary);
     }
 
     @Test