bonjour
(2x+1)² - ( 2x-1)² = ( 4x² + 4x + 1 ) - ( 4x² - 4x + 1 )
= 4x² + 4x + 1 - 4x² + 4x - 1 = 4x + 4x = 8x
2019² - 2017² = ( 2019 - 2017 ) ( 2019 + 2017 )
= 8072
