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) 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