Réponse :

Bonjour

Exercice 19

a) (x + 4)² = x² + 8x + 16

b) (10x - 5)² = 100x² - 100x + 25

c) (2x + 3)² = 4x² + 12x + 9

d) (x - 4)(x + 4) = x² - 16

e) (7x + 1)(7x - 1) = 49x² - 1

Exercice 20

a) (x+ 4)² = x² + 8x + 16

b) (x - 5)² = x² - 10x + 25

c) (1 + 3x)(1 - 3x) = 1 - 9x² = -9x² + 1

d) (5 + 2x)(-2x + 5) = 25 - 4x² = -4x² + 25

Exercice 21

a) (x + 6)² = x² + 12x + 36

b) (x - 3)² = x² - 6x + 9

c) (4 + 8x)² = 64x² + 64x + 16

d) (6 - 2x)² = 4x² - 24x + 36

e) (5 + 9x)(5 - 9x) = 25 - 81x² = -81x² + 25

f) (7 + 4x)(-4x + 7) = 49 - 16x² = -16x² + 49