Bonsoir,

1.

a) 2/3 - 7/5

On réduit au même dénominateur :

2/3 = (2 * 5)/(3 * 5) = 10/15

7/5 = (7 * 3)/(5 * 3) = 21/15

10/15 - 21/15 = (-11)/15

b) 2/3 + 5/4 + 7/2

On réduit au même dénominateur :

2/3 = (2 * 4 * 2)/(3 * 4 * 2) = 16/24

5/4 = (5 * 2 * 3)/(4 * 2 * 3) = 30/24

7/2 = (7 * 4 * 3)/(2 * 4 * 3) = 84/24

16/24 + 30/24 + 84/24 = 130/24 = 65/12

c) (-3)/10 * (-4) * 2/3

(-3 * -4 * 2)/(10 * 1 * 3) = 24/30

2)

a) 4x - 4 = 8

4x = 4 + 8

4x = 12

x = 12 / 4 = 3

b) 3x + 2 = 6x - 1

3x - 6x = (-2) - 1

-3x = (-3)

x = (-3)/(-3) = 1

3)

a) x(2 - x) = 2x - x²

b) (x - 4)(-3x - 3) = -3x² - 3x + 12x + 3= -3² - 15x + 3