bonjour
A = ( 7 x - 3 )² - ( 8 x + 5 ) ( 7 x - 3 )
A = ( 49 x² - 42 x + 9 ) - ( 56 x² - 24 x + 35 x - 15 )
A = 49 x² - 42 x + 9 - 56 x² + 24 x - 35 x + 15
A = - 7 x ² - 53 x + 24
A = ( 7 x - 3 ) ( 7 x - 3 - 8 x - 5 )
= ( 7 x - 3 ) ( - x - 8 )
x = 0
A = - 3 * - 8 = 24
x = - 7
A = - 52 * - 1 = 52