Réponses

2013-12-06T17:43:58+01:00
Exercice 1
a. 2/7 et 3/10
dénominateur commun 70=7*10
(2*10)/(7*10) = 20/70
et (3*7)/(10*7) = 21/70

b.-2.3/2 et 3.61/5
dénominateur commun 10=2*5
(-2.3*5)(2*5) = -11.5/10
(3.61*2)/(5*2) =  7.22/10

c. 1/2;-4/5 et 7/15
dénominateur commun 30 = 2*3*5
1/2 = (1*3*5)/(2*3*5) = 15/30
-4/5 = (-4*2*3)/(5*2*3) = -24/30
7/15 = (7*2)/(15*2) = 14/30

d. -10.34/24 et 15.2/16
dénominateur commun 96=4*4*6=24*4=16*6
-10.34/24=(-10.34*4)/(24*4) = 41.36/96
15.2/16 = (15.2*6)/(16*6) = 91.2/96

e. 5/6; 1/-12 et 5/24
dénominateur commun 24=6*4=12*2
5/6= (5*6)(4*6) = 30/24
1/-12 = -1/12 =(-1*2)(12*2) = -2/24
et 5/24

f.32/15; 1/20; -17/12 et 19/6=38/12
dénominateur commun 180=3*5*12=15*12=20*9
32/15 = 32*12/15*12 = 384/180
1/20 = 9/20*9 = 9/180
-17/12 = (-17*3*5)/12*3*5 = -255/180
19/6=38/12 = 38*3*5/12*3*5 = 570/180

Exerccie 2
A= -(9/5)+(7/5) = (-9+7) / 5 =-2/5
B = -(8/7)-(12/7) = (-8-12)/7 = -20/7
C = -2.62 / 27 + (-14.5)/27 = (-262-14.5)/27 = -17.2/27
D = 12/25 - (-17/25) + (-133/25) = (12+17-133)/25 = -104/25

Exxercice 3
A = 3+3/2 = 3*2/2 +3/2 = 6/2+3/2 = (6+3)/2 = 9/2
B = 4.5-7/8 = 4.5*8/8 -7/8 = 36/8-7/8 = (36-7)/8 = 29/8
C = 5 + 6/-5 = 5*5/5-6/5 = (25-6)/5 = 19/5
D = -(2/7)+3/14 = (-2*2)/(7*2) + 3/14 = (-4+3)/14 = -1/14
E = -5/21-7/3 = -5/21-(7*7)/(3*7) = (-5-49)/21 = -54/21 = -(3*18)/(3*7) = -18/7
F = 1/17-5/51 = 51/17*51 - 5*17/51*17 = (51-85)/867 = -34/867 = -(2*17)/(51*17) = -2/51