Bonjour
exercice 1 :
A = (5/(13 - 55))/((21 - 16)/56)
A = (5/(-42)) / (5/56)
A = -5/42 x 56/5
A = -5/5 x 56/42
A = (-1) x (8 x 7)/(6 x 7)
A = (-1) x 8/6
A = -1 x (2 x 4)/(2 x 3)
A = -4/3
Exercice 2 :
B = (10^(-2) x 10^3)/(10^7 x 10^(-9))
B = 10^(-2+3-7+9)
B = 10^(-9+12)
B = 10^3
Exercice 3 :
3 micro de 7 nano de 2 Giga
N = 3 x 10^(-6) x 7 x 10^(-9) x 2 x 10^6
N = 42 x 10^(-6-9+6)
N = 42 x 10^(-9)
N = 4,2 x 10^(-8)
Exercice 4 :
C = 0,0071 x 10^3
notation scientifique :
C = 7,1 x 10^(-3) x 10^3
C = 7,1 x 10^(-3+3)
C = 7,1 x 10^0