Réponse :
Je remplace les x par des y dans tes équations pour les différencier du signe x (multiplier).
A = 3 ( y + 8 ) + 4 ( 7y + 2 )
= ( 3y + 3 x 8 ) + (4 x 7y + 4 x 2)
= (3y + 24 ) + ( 28y + 8 )
= 3y + 24 + 28y + 8 (= 3y+28y + 24+8)
= 31y + 32
B = 5 ( y - 1 ) - 7y ( 2 + 3y )
= 5y - 5x1 - 7y x 2 - 7y x 3y
= 5y - 5 - 14y - 21y²
= -9y -21y² - 5
C = 2y ( 4 - 5y ) - ( y - 7 )
= (2y x 4 - 2y x 5y ) - y + 7
= 8y - 10y² - y + 7
= 7y - 10y² + 7
D = ( 3 - 8y ) - 5 ( 4y - 7 )
= 3 - 8y - (5 x 4y - 5 x 7 )
= 3 - 8y - 20y + 35
= -28y + 38
E = 7 ( 3 - 2y ) - 4y ( 2y - 1)
= 7 x 3 + 7 x (-2y) - 4y x 2y - 4y x (-1)
= 21 - 14y - 8y² + 4y
= 21 - 10y - 8y²
F = 7y - 5 ( 2 - 9y ) + 7 ( 9y - 1 )
= 7y - (5 x 2 + 5x (-9y) ) + (7 x 9y + 7 x (-1) )
= 7y - ( 10 - 45y ) + ( 63y - 7 )
= 7y - 10 + 45y + 63y - 7
= 115y - 17
