Ex 3

1. B = (5x-2)² + (5x-2)(3x+7)

B = 25x² - 20x + 4 + 15x² + 35x - 6x - 14

B = 40x² + 9x - 10

3. (5x-2)(8x+5) = 0

5x-2 = 0 ou 8x+5 = 0

5x = 0+2 8x = 0-5

x = 2÷5 x = -5÷8

x = 0,4 x = -40

Ex 4

1. C = (6x-7)² - (2x-3)²

C = 36x² - 84x + 49 - 4x² - 12x + 9

C = 32x² - 96x + 58

3. (4x-4)(8x-10) = 0

4x-4 = 0 ou 8x-10 = 0

4x = 0-4 8x = 0+10

x = -4÷4 x = 10÷8

x = -1 x = 1,25