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class Squares
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@num
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def initialize(num)
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@num = num
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end
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def difference
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square_of_sum - sum_of_squares
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end
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def sum_of_squares
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(1..@num).map{|n| n ** 2}.inject(&:+)
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end
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def square_of_sum
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(1..@num).inject(&:+) ** 2
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end
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end
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module BookKeeping
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VERSION = 4
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end
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