Réponses

2013-03-07T18:39:54+01:00

1.

 

2x+3=0

2x=-3

x=-3/2

x=-1.5

 

2.

 

x/6+5=0

x/6+30/6=0

x+30=0

x=-30

 

3.

 

-4x+15=8x

-4x-8x=-15

-12x=-15

x=15/12

 

4.

 

8x+9=5x-6

8x-5x=-6-9

3x=-15

x=-15/3

x=-5

 

5.

 

5(x+9)=50

5*x+5*9=50

5x+45=50

5x=50-45

5x=5

x=5/5

x=1

 

6.

 

2x/3+2=-3

2x/3+6/3=-9/3

2x+6=-9

2x=-9-6

2x=-15

x=-15/2

x=-7.5

 

7.

 

7(x+9) = 3(x-2)

7*x+7*9=3*x+3*(-2)

7x+63=3x-6

7x-3x=-6-63

4x=-69

x=-69/4

x=-17.25

 

 

2013-03-07T18:53:47+01:00

1) 2x + 3 = 0

2x = -3

x = -3/2 ( équivalent à 1,5 )

 

2) x/6 + 5 = 0

x/6 + 5x6/1x6 = 0

x/6 + 30/6 = 0

x + 30 = 0

x = -30

 

3) -4x +15 = 8x

15 = 8x + 4x

15 = 12x

15/12 = x

x = 5/4

 

4) 8x + 9 = 5x - 6

8x - 5x = -6 -9

3x = -15

x = -15/3

x = -5

 

5) 5(x+9) = 50

5x + 45 = 50

5x = 50 - 45

5x = 5

x = 5/5

x = 1

 

6) 2x/3 +2 = -3

2x/3 +2x3/1x3 = -3x3/1x3

2x +6 = -9

2x = -9 -6

2x = -15

x = -15/2

 

7) 7(x+9) = 3(x-2)

7x +63 = 3x -6

7x -3x = -6 -63

4x = -69

x = -69/4