# Difference Of Squares

Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.

The square of the sum of the first ten natural numbers is
(1 + 2 + ... + 10)² = 55² = 3025.

The sum of the squares of the first ten natural numbers is
1² + 2² + ... + 10² = 385.

Hence the difference between the square of the sum of the first
ten natural numbers and the sum of the squares of the first ten
natural numbers is 3025 - 385 = 2640.


## Running the tests

1. Go to the root of your PHP exercise directory, which is `<EXERCISM_WORKSPACE>/php`.
   To find the Exercism workspace run

        % exercism debug | grep Workspace

1. Get [PHPUnit] if you don't have it already.

        % wget --no-check-certificate https://phar.phpunit.de/phpunit.phar
        % chmod +x phpunit.phar

2. Execute the tests:

        % ./phpunit.phar difference-of-squares/difference-of-squares_test.php

[PHPUnit]: http://phpunit.de


## Source

Problem 6 at Project Euler [http://projecteuler.net/problem=6](http://projecteuler.net/problem=6)

## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.