Bonjour !
A = 49-9x²+(-7-3x)(8-41)
Développer et réduire :
49-9x²-56+287-24x+123x
A = -9x²+99x+182
Factoriser :
A = 7²- 9x²+(-7-3x)(8-41)
A = (7-3x)(7+3x)+(-7-3x)(8-41)
A = (7-3x)(7+3x)+(7+3x)(8-41)
A = (7+3x)(7-3x+8-41)
A = (7+3x)(-3x-26)
Calculer À pour x = 9
A = (7+3x)(-3x-26) = (7+3×9)(-3×9-26)
(7+27)(-27-26)
(34)(-43) = - 1 462
Pour A = 0
(7+3x)(-3x-26) = 0
(7+3x) = 0 => x = - 7/3
(-3x-26) = 0 => x = -26/3
Pour A = -7
7+3x= -7 => x = - 14/3
-3x-26 = - 7 => x = 16/3
Bon courage.
