Réponse :
Bonjour,
Explications étape par étape
Ex1 :
A = 4/7-2 / 2-11/4
A = 4/7 - 14/7 / 8/4 - 11/4
A = -10/7 / -3/4
A = -10/7 × (-4)/3
A = 40/21
B = 2 × (10^3)^4 × 10^-8 / 40 × 10^-2 × 1/5
B = 2/40 × 1/5 × 10^12 × 10^-8/10^-2
B = 2/40/5 × 10^((12+(-8))/10^-2
B = 2/8 × 10 ^4/10^-2
B = 1/4 × 10^4-(-2)
B = 1/4 × 10^6
B = 0.25 × 10^6
B = 2.5 × 10^5
C = (2/5 / 8/15) / (4/7 / 5/21)
C = (2/5 × 15/8) / (4/7 × 21/5)
C = (2×5×3 /5×4×2) / (4×7×3 /7×5)
C = (3/4) / (12/5)
C = 3/4 × 5/12
C = 3×5 / 4×4×3
C = 5/16
C = 0.3125
Ex 2 :
1) développer et réduire D
D = (2x-3)^2 - 3(2x -3)
D = 4x^2 - 2 ×2x×3+9 -6x+9
D = 4x^2 - 18x + 18
2) factoriser D
D = (2x-3)(2x-3) - 3(2x-3)
D = (2x-3)[(2x-3)-3]
D = (2x-3)(2x-6)
3) calculer D pour x = 2
D = (2x-3)(2x-6)
D = ( 2 × 2 -3)(2 × 2 -6)
D = (4-3)(4-6)
D = 1 × (-2)
D = -2
4) D = 0
(2x -3)(2x-6) = 0
2x - 3 = 0 ou 2x - 6 = 0
2x = 3 ou 2x = 6
X = 3/2 ou x = 6/2 = 3
S = {3/2 ; 3}
