EQUATION: bjr, j'ai deux exercices de maths de niv 3è ou il faut calculer: -x+8= -5x 4[tex] x^{2} [/tex]+16x= 6(4x+10)

Bonjour,

-x + 8 = -5x
5x - x = -8
4x = -8
x = -8/4
x = -2

4x^2 + 16x = 6(4x + 10)
4x^2 + 16x - 24x - 60 = 0
4x^2 - 8x - 60 = 0
4(x^2 - 2x - 15) = 0

x^2 - 2x - 15 = 0

On pose x = X + 1 :

(X + 1)^2 - 2(X + 1) - 15 = 0
X^2 + 2X + 1 - 2X + 2 - 15 = 0
X^2 - 12 = 0
X^2 = 12
X = V12 ou X = -V12
X = 2V3 ou X = -2V3

x = X + 1
x = 2V3 + 1
Ou
x = -2V3 + 1