2.2. Function. Рассчитать значение по формуле

src/main/java/ru/job4j/lambda/FunctionFormula.java

@@ -0,0 +1,14 @@
+package ru.job4j.lambda;
+
+import java.util.function.Function;
+
+public class FunctionFormula {
+
+    public static double calculate(double x) {
+        return calculate(f -> Math.pow(f, 2) + 2 * f + 1, x);
+    }
+
+    public static double calculate(Function<Double, Double> y, double x) {
+        return y.apply(x);
+    }
+}

src/test/java/ru/job4j/lambda/FunctionFormulaTest.java

@@ -0,0 +1,15 @@
+package ru.job4j.lambda;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class FunctionFormulaTest {
+
+    @Test
+    public void test() {
+        assertEquals(1, FunctionFormula.calculate(0), 0.01);
+        assertEquals(4, FunctionFormula.calculate(1), 0.01);
+        assertEquals(9, FunctionFormula.calculate(2), 0.01);
+    }
+}