a = 18 x 19 + 20 x 21 - 22 x 23 + 2 x [ 15 + 3 x ( 40² - 49² ) ]
a = 342 + 420 - 506 + 2 x [ 15 + 3 x ( 1 600 - 2 401 ) ]
a = 762 - 506 + 2 x [ 15 + 3 x ( - 801 ) ]
a = 256 + 2 x ( 15 - 2 403 )
a = 256 + 2 x ( - 2388 )
a = 256 - 4 776
a = - 4 520
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b = 2013 x 2012 + 2013 x 2011 - 2013 x 2022 + 7 x [ 9 + 2 x ( 53² - 52²)
b = 2013 x ( 2012 + 2011 - 2022 ) + 7 x [ 9 + 2 x ( 2 809 - 2 704 ) ]
b = 2013 x ( 2023 - 2022 ) + 7 x ( 9 + 2 x 105 )
b = 2013 x 1 + 7 x ( 9 + 210 )
b = 2013 + 7 x 219
b = 2013 + 1 533
b = 3546
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a = - 4 520 si b = 3 546 ⇒ a < b