Bonjour,
a. Proposer une écriture plus simple de chaque expression littérale ,sans signe x.
A=3*x+5 = 3x + 5
B=8-2*x = 8 - 2x
C=4*(2*x-3) =8x - 12
D = x*4 x (1*x-1) = 4x * (x - 1) = 4x² - 4x
E = (x * 5 - 3 )*x*2 = (5x - 3) * 2x = 10x² - 6x.
b.Calculer chaque expression pour x=3 ,
3x + 5 = 3 * 3 + 5 = 9 + 5 = 14
8 - 2x = 8 - 2 * 3 = 8 - 6 = 2
8x - 12 = 8 * 3 - 12 = 24 - 12 = 12
4x² - 4x = 4 * 3² - 4 * 3 = 4 * 9 - 12 = 36 - 12 = 24
10x² - 6x = 10 * 3² - 6 * 3 = 10 * 9 - 18 = 90 - 18 = 72
Puis pour x=-2
3x + 5 = 3 * - 2 + 5 = - 6 + 5 = - 1
8 - 2x = 8 - 2 * - 2 = 8 + 4 = 12
8x - 12 = 8 * - 2 - 12 = - 16 - 12 = - 28
4x² - 4x = 4 * (- 2)² - 4 * (- 2) = - 4 * 4 + 8 = - 16 + 8 = - 8
10x² - 6x = 10 * (- 2)² - 6 * (- 2) = 10 * 4 + 12 = 40 + 12 = 52.
