Exercice 3
a) 43 234.78 = 4.323478×10^4
b) 34.875×10^-3 = 0.034875 = 3.4×10^-2
c) 6×2/3 = 12/3 = 4
10^6 × 10^-4 = 10^(6-4) = 10^2
(10^5)² = 10^(5×2) = 10^10
4×10^2/10^10 = 4×10^(2-10) = 4×10^(-8)
Exercice 4
7/3 + -4/3 = (7-4)/3 = 3/3 = 1
-1/5 - - 3/5 = (-1 - (-3))/5 = (-1 + 3)/5 = 2/5
11/12 + 5/3 = 11/12 + (5×4)/(3×4) = 11/12 + 20/12 = 31/12
5/8 - -2/4 = 5/8 - (-2×2)/(4×2) = 5/8 - -4/8 = (5- -4)/8 = (5+4)/8 = 9/8
2/3 + -5/8 = (2×8)/(3×8) + (-5×3)/(8×3) = 16/24 + -15/24 = (16-15)/24 = 1/24
-5/6 + -7/4 = (-5×2)/(6×2) + (-7×3)/(4×3) = -10/12 + -21/12 = (-10 - 21)/12 = -31/12
2 + 5/3 = 2/1 + 5/3 = (2×3)/(1×3) + 5/3 = 6/3 + 5/3 = (6+5)/3 = 11/3
Exercice 5
-3/5 × 4/-5 = (-3×4)/(5×-5) = -12/-25
-1/3 × -5/-2 = (-1×-5)/(3×-2) = 5/-6 = -5/6
5/3 × -4/5 = -4/3 (on simplifie par 5 en haut et en bas)
-12/-7 × -21/-8 = (-12×-21)/(-7×-8)
= (-3×4×3×-7)/(-7×-2×4)
= (-3×3)/(-2) on simplifie par 4 et -7 en haut et en bas
= -9/-2
= 9/2
-63/25 × 40/-81 = (-63×40)/(25×-81)
= (7×-9×5×8)/(5×5×-9×9)
= (7×8)/(5×9) on simplifie par 5 et -9 en haut et en bas
= 56/45
Voilà ! :)
