bonjour
A (x) = ( x - 3 ) ( 2 x - 7) - ( 4 x + 2 ) ( x - 3 )
A (x) = 2 x² - 7 x - 6 x + 21 - ( 4 x² - 12 x + 2 x - 6 )
A (x) = 2 x² - 13 x + 21 - 4 x² + 10 x + 6
A (x) = - 2 x² - 3 x + 27
A (x) = ( x - 3 ) ( 2 x - 7 - 4 x - 2 )
A (x) = ( x - 3 ) ( - 2 x - 9 )
A (x) = 0 pour x = 3 ou x = - 9/2