Уравнения с двумя корнями

levelp · May 23, 2015 · 9a243cb · 9a243cb
1 parent bf5c184
commit 9a243cb
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diff --git a/src/main/java/QuadraticEquation.java b/src/main/java/QuadraticEquation.java
@@ -12,6 +12,11 @@ public class QuadraticEquation {
      * @return корни уравнения (значения x)
      */
     public static double[] solve(double a, double b, double c) {
-        return new double[]{-b / (2 * a)};
+        // Дискриминант
+        double D = Math.pow(b, 2) - 4 * a * c;
+        if (D == 0)
+            return new double[]{-b / (2 * a)};
+        double d = Math.sqrt(D);
+        return new double[]{(-b - d) / (2 * a), (-b + d) / (2 * a)};
     }
 }
diff --git a/src/test/java/QuadraticEquationTest.java b/src/test/java/QuadraticEquationTest.java
@@ -16,4 +16,12 @@ public void testSimpleOneRoot() {
         assertArrayEquals("(x-1)^2 = x^2-2x+1", new double[]{1}, QuadraticEquation.solve(1, -2, 1), EPS);
         assertArrayEquals("2(x-1)^2 = 2x^2-4x+2", new double[]{1}, QuadraticEquation.solve(2, -4, 2), EPS);
     }
+
+    /**
+     * Уравнения с двумя корнями
+     */
+    @Test
+    public void testTwoSolutions() {
+        assertArrayEquals("(x-1)(x-2) = x^2-3x+2", new double[]{1, 2}, QuadraticEquation.solve(1, -3, 2), EPS);
+    }
 }