Sagot :
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