Bonjour,
Exercice 24 :
[tex](2x + 3)(x + 1) = 2 {x}^{2} + 2x + 3x + 3 = 2 {x}^{2} + 5x + 3[/tex]
[tex](x + 3)(2x + 1) = 2 {x}^{2} + x + 6x + 3 = 2 {x}^{2} + 7x + 3[/tex]
[tex](2x - 1)(3 - x) = 6x - 2 {x}^{2} - 3 + x = - 2 {x}^{2} + 7x - 3[/tex]
[tex](3 - 2x)(x - 1) = 3x - 3 - 2 {x}^{2} + 2x = - 2 {x}^{2} + 5x - 3[/tex]
Exercice 27 :
Forme factorisée de f(x) :
f(x) = 2x(x + 1) - x(x - 4)
f(x) = x(2(x + 1) - (x - 4))
f(x) = x(x + 6)
Développer f(x) :
2x(x + 1) - x(x - 4)
[tex] = 2 {x}^{2} + 2x - {x}^{2} + 4x[/tex]
[tex] = {x}^{2} + 6x[/tex]
Résoudre f(x) = 0
x(x + 6) = 0
2 solutions
x = 0 ou x + 6 = 0 => x = - 6
S{- 6 ; 0}
