1) on a : a = 3/5 b = 10/21 calculer a+b ; a-b ; ab

2)calcule chaque expresion en detaillents :A= 3/8 x (4/9+2/3) B= 7/5x3/10+1/5

3)calculer :A = 8-(5+2)-9 et B =(-3+4)-(-7+6)+(-8-2)

4)developer et reduire: x(2x-3)+2x(4-x)

1

Réponses

2013-06-23T22:32:45+02:00

1)    a + b   =  3/5 + 10/21   =   63/105 + 50/105   =   113/105

 

       a - b   =  3/5 - 10/21   =   63/105 - 50/105   =   13/105

 

       a × b   =   3/5 × 10/21   =   1/1 × 2/7   =   2/7

 

 

 

2)   A = 3/8 × (4/9 + 2/3)   =   3/8 × (4/9 + 6/9)   =   3/8 × 10/9   =   1/4 × 5/3   =   5/12

      

      B = 7/5 × 3/10 + 1/5   =   21/50 + 10/50   =   31/50

 

 

 

3)   A = 8 - (5 + 2) - 9   =    8 - 7 - 9   =   8 - 16   =   -8

 

      B = (-3 + 4) - (-7 + 6) + (-8 - 2)   =   1 - (-1) + (-10)   =   1 + 1 - 10   =   2 - 10   =   -8

 

 

 

4)  x (2x - 3) + 2x (4 - x)   =   2x² - 3x + 8x - 2x²   =   5x