Bonjour pourriez vous m’aidez pour ce dm svp

Bonjour, 
Exercice 2 : 
1. x ∈ [ -1, 2 ]
2. x ∈ ] -4, 2 ]
3. x ∈ ] 5, 2 [
4. x ∈ [ - 3, + infini [
5. x ∈ ] - infini, -5]

Exercice 3 
A(x) = 2x ( 3x - 4) = 2x *3x - (2x * 4) = 6x² - 8x
B(x) = 5x (2x + 7) = 5x * 2x + 5x * 7 = 10x² + 35x 
C(x) = ( 3x +1 ) (2x - 3 ) = 3x * 2x - 3x * 3 + 1 * 2x - 3 *1 = 6x² - 9x + 2x - 3 = 6x² - 7x - 3 
D(x)= (2 - 3x) (5- 4x) = ( 2 * 5 - 2 * 4x) - (3x* 5 - 3x * (-4x)) = ( 10 - 6x - 15x +12x ² = 12x² - 23x + 10 

Exercice 4 
A = (3x +5)² = 3x² + 2*3x*5 + 5² = 9x² + 30x + 25
B= ( 5x - 3 )² = 5x² - 5x*2*3 + 3² = 25x² - 15x + 9 
C= ( 2x-7)(2x+7) = 2x² - 7² = 4x² - 49 

Exercice 5 
D= 49x² + 84x + 36 = ( 7x + 6) ²
E= x² - 18x + 81 = (x - 9)²
F= 16x² - 25y² = ( 4x - 5y) (4x + 5y ) 

Voila !