Réponses

2014-02-04T18:33:02+01:00
1) 8x-3 = 2x+9
6x = 12
x = 2

Je remplace x par 2 :

8*2-3 = 2*2+9
16-3 = 4+9
13 = 13

2) -3x-13 = 8x-5
-11x = 8
x = -(8/11)

Je remplace x par -(8/11) :

-3*-(8/11)-13 = 8*-(8/11)-5
(24/11)-13 = -(64/11)-5
(24/11)-(143/11) = -(64/11)-(55/11)
-(119/11) = -(119/11)

3) 3(-1-2t) = 4(1-5t) 
-3-6t = 4-20t
14t = 7
t = 7/14
t = 1/2

Je remplace t par 1/2 :

3(-1-2*(1/2)) = 4(1-5*(1/2)) 
3(-1-1) =  4(1-5/2)
3*(-2) = 4((2/2)-(5/2))
-6 = 4*(-3/2)
-6 = -12/2
-6 = -6