freeCodeCamp/guide/english/certifications/coding-interview-prep/project-euler/problem-6-sum-square-difference/index.md

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Sum square difference

Problem 6: Sum square difference

Method:

• Sum of first n natural numbers can be calculated by using this formula:

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• Sum of squares of n natural numbers can be calculated by using this formula:

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• We can calculate the values using the above formula and subtract them to get the result.

Solution:

function sumSquareDifference(n) {
  const sumOfN = (n*(n+1))/2;
  const sumOfNSquare = (n*(n+1)*(2*n+1))/6;
  
  //** is exponentaial operator added in ES7, it's equivalent to Math.pow(num, 2)`
  return (sumOfN ** 2) - sumOfNSquare;
}

References:

• Sum of n numbers - Wikipedia
• Sum of n square numbers - Wikipedia