Je doit faire l'exercice 23,24,25 aidez moi svp

Exercice 23 :

a) (3 - 4x)² = 
3² - 2 * 3 * 4x + (4x)² = 
9 - 24x + 16x²

b) (10 + 9x) (10 - 9x) = 
10² - (9x)² = 
100 - 81x²

c) (3y + 6)² = 
(3y)² + 2 * 3y * 6 + 6² = 
9y² + 36y + 36

d) (8x - 6y) (8x + 6y) = 
(8x)² - (6y)² = 
64x² - 36y²

Exercice 24 :

a) (3 + 2x)² = 
3² + 2 * 3 * 2x + (2x)² = 
9 + 12x + 4x²

b) (3 + 2x) (3 - 2x) = 
3² - (2x)² = 
9 - 4x²

c) (3 - 2x)² = 
3² - 2 * 3 * 2x + (2x)² =
9 - 12x + 4x²

d) (2x - 3) (2x + 3) = 
(2x)² - 3² = 
4x² - 9

Exercice 25 :

A = (x + 2)² + 9
A = x² + 2 * x * 2 + 2² + 9
A = x² + 4x + 4 + 9
A = x² + 4x + 13

B = (2x + 1)² - x + 3
B = (2x)² + 2 * 2x * 1 + 1² - x + 3
B = 4x² + 4x + 1 - x + 3
B = 4x² + 3x + 4

C = (3x - 2)² - 5 (x + 3)
C = (3x)² - 2 * 3x * 2 + 2² - 5 * x - 5 * 3
C = 9x² - 12x + 4 - 5x - 15
C = 9x² - 17x - 11

D = (x + 5)² + 3 (x + 6)
D = x² + 2 * x * 5 + 5² + 3 * x + 3 * 6
D = x² + 10x + 25 + 3x + 18
D = x² + 13x + 43

Les * désignent "fois".

Bonsoir , 
Ex23 : 
(3-4x)²                                         ⇒ (a-b)² = a² + b² - 2ab
= 3² + (4x)² - 2 × 3 × 4x
= 9 + 16x² - 24x
(10+9x) (10-9x)                        ⇒ (a+b) (a-b) = a² - b² 
= 10² - (9x)²
= 100 - 81x
(3y+6)²
= (3y)² + 6² + 2 × 3y × 6
= 9y² + 36 + 36y
(8x-6y) (8x+6y)
= (8x)² - (6y)²
= 64x² - 36y²
Ex24 : 
(3+2x)²
= 3² + (2x)² + 2 × 3 × 2x
= 9 + 4x² + 12x
(3+2x) (3-2x)
= 3² - (2x)²
= 9 - 4x²
(3-2x)²
= 3² + (2x)² - 2 × 3 × 2x
= 9 + 4x² - 12x
(2x-3) (2x+3)
= (2x)² - 3²
= 4x² - 9 
Ex25 : 
A = (x+2)² + 9 
A = x² + 2² + 2 × x ×2 + 9
A = x² + 4 + 4x + 9
A = x² + 4x + 13
B = (2x+1)² - x + 3 
B = (2x)² + 1² + 2 × 2x × 1 - x + 3 
B = 4x² + 1 + 4x - x + 3
B = 4x² + 3x + 4 
C = (3x-2)² - 5(x+3)
C = (3x)² + 2² - 2 × 3x × 2 - (5x+15)
C = 9x² + 4 - 12x - 5x - 15
C = 9x² - 17x - 11
D = (x+5)² + 3(x+6)
D = x² + 5² + 2 × x × 5 + 3x + 18
D = x² + 25 + 10x + 3x + 18
D = x² + 13x + 43