bonjour
f(x)= (3x+7)(-x+8)-(3x+7)(2x+5).
f (x) = - 3 x² + 24 x - 7 x + 56 - ( 6 x² + 15 x + 14 x + 35 )
f ( x) = - 3 x² + 17 x + 56 - 6 x² - 29 x - 35
f ( x) = - 9 x² - 12 x + 21
f (x) = (3 x + 7) ( - x + 8 - 2 x - 5 )
F ( x) = ( 3 x + 7 ) ( - 3 x + 3 )
F ( 1) = ( 3 + 7 ) ( - 3 + 3) = 0
F ( - 2) = ( - 6 + 7 ) ( 6 + 3 ) = 9
