*Find the sum of the roots of a quadratic equation

//https://www.codewars.com/kata/57d448c6ba30875437000138/train/javascript

function roots(a,b,c){
  let d = b ** 2 - 4 * a * c;
  if (d >= 0) {
    let x1 = (-b + Math.sqrt(d)) / (2 * a);
    let x2 = (-b - Math.sqrt(d)) / (2 * a);
    return +(x1 + x2).toFixed(2);
  } else {
    return null;
  }
}