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37 changes: 37 additions & 0 deletions Maths/QuadraticRoots.js
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/**
* @see https://www.cuemath.com/algebra/roots-of-quadratic-equation/
* @author Dibya Debayan Dash
* Calculates the roots of a quadratic equation of the form ax^2 + bx + c = 0.
*
* @param {number} a - Coefficient of x^2.
* @param {number} b - Coefficient of x.
* @param {number} c - Constant term.
* @returns {number[]} - An array containing the roots if they are real,
* or an empty array indicating no real roots.
*
* @example
* // Find the roots of the quadratic equation: 2x^2 - 4x + 2 = 0
* const roots = quadraticRoots(2, -4, 2);
* // Expected output: [1]
*/
const quadraticRoots = (a, b, c) => {
// Calculate the discriminant
const discriminant = b * b - 4 * a * c

// Check if roots are real
if (discriminant < 0) {
return []
} else if (discriminant === 0) {
// One real root
return [-b / (2 * a)]
} else {
// Two real roots
const sqrtDiscriminant = Math.sqrt(discriminant)
return [
(-b + sqrtDiscriminant) / (2 * a),
(-b - sqrtDiscriminant) / (2 * a)
]
}
}

export { quadraticRoots }
13 changes: 13 additions & 0 deletions Maths/test/QuadraticRoots.test.js
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import { quadraticRoots } from '../QuadraticRoots.js'

describe('quadratic roots', () => {
it('returns an array with two real roots when the discriminant is positive', () => {
expect(quadraticRoots(1, -3, 2)).toEqual([2, 1])
})
it('returns an array with one real root when the discriminant is zero', () => {
expect(quadraticRoots(1, -2, 1)).toEqual([1])
})
it('returns an empty array indicating no real roots when the discriminant is negative', () => {
expect(quadraticRoots(1, 2, 5)).toEqual([])
})
})