algorithm: quadratic formula

DIRECTORY.md

@@ -193,6 +193,7 @@
   * [PowLogarithmic](Maths/PowLogarithmic.js)
   * [PrimeCheck](Maths/PrimeCheck.js)
   * [PrimeFactors](Maths/PrimeFactors.js)
+  * [QuadraticFormula](Maths/QuadraticFormula.js)
   * [RadianToDegree](Maths/RadianToDegree.js)
   * [ReverseNumber](Maths/ReverseNumber.js)
   * [ReversePolishNotation](Maths/ReversePolishNotation.js)

Maths/QuadraticFormula.js

@@ -0,0 +1,32 @@
+/**
+ * @function quadraticFormula
+ * @description This script will find the the roots of a quadratic equation.
+ * @param {number} a
+ * @param {number} b
+ * @param {number} c
+ * @return {array}
+ * @see https://en.wikipedia.org/wiki/Quadratic_formula
+ * @example quadraticFormula(1, -3, -4) = [4, -1]
+ * @example quadraticFormula(1, 5, 6) = [-2, -3]
+ * @example quadraticFormula(1, -3, 8) = []
+ */
+
+const solveQuadraticEquation = (a, b, c) => {
+  if (typeof a !== 'number' || typeof b !== 'number' || typeof c !== 'number') {
+    return new TypeError('Some argument is not a number.')
+  }
+  const discriminant = (b ** 2) - (4 * a * c)
+  const denominator = 2 * a
+  let answer = []
+  if (discriminant > 0) {
+    const x1 = (-b + Math.sqrt(discriminant)) / denominator
+    const x2 = (-b - Math.sqrt(discriminant)) / denominator
+    answer = [x1, x2]
+  } else if (discriminant === 0) {
+    const x = (-b) / denominator
+    answer = [x]
+  }
+  return answer
+}
+
+export { solveQuadraticEquation }

Maths/test/QuadraticFormula.test.js

@@ -0,0 +1,9 @@
+import { solveQuadraticEquation } from '../QuadraticFormula'
+
+test('Quadratic Equation', () => {
+  expect(solveQuadraticEquation(1, -3, -4)).toStrictEqual([4, -1])
+  expect(solveQuadraticEquation(1, 5, 6)).toStrictEqual([-2, -3])
+  expect(solveQuadraticEquation(3, 24, 48)).toStrictEqual([-4])
+  expect(solveQuadraticEquation(1, -3, 8)).toStrictEqual([])
+  expect(solveQuadraticEquation(1, -2, 9)).toStrictEqual([])
+})