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Sagot :

bonjour

1

comme (a-b)² = a²-2ab+b²

et que (a+b) (c+d) = ac+ad+bc+bd

on aura

A(x) = 9x²-12x+4 - (6x²+15x-4x-10)

      = 3x²-23x+14

2

A(x) = (3x-2) (3x-2) - (3x-2) (2x+5)

       = (3x-2) [(3x-2) - (2x+5)]

       = (3x-2) (x-7)

3

(3x-2) (x-7)=0

x=2/3 ou x=7

4

A(-2/3) = (3*(-2/3)-2) (-2/3-7) = -4 * (-2/3-21/3) = -4 * (-23/3) = 92/3

INEQUATION

Bonjour,

A(x)= (3x-2)²-(3x-2)(2x+5)

Développer:

A(x)= 9x²-6x-6x+4-(6x²-4x+15x-10)= 9x²-12x+4-6x²-11x+10= 3x²-23x+14.

Factoriser:

A(x)= (3x-2)(3x-2)-(3x-2)(2x+5)

A(x)= (3x-2)(3x-2-2x-5)

A(x)= (3x-2)(x-7)

Résoudre A(x):

(3x-2)(x-7)= 0

3x-2= 0  ou  x-7= 0

x= 2/3           x= 7

Calculer A(-2/3):

A(-2/3)= 3(-2/3)²-23(-2/3)+14  utilise la calculette

A(-2/3)= 92/3

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