qui peut me resoudre cet exercice niveau 3eme?

1) A = ( x-5 )² + ( 2x+3 )( x-5 )
= x² - 10x + 25 + 2x² - 10x + 3x - 15
A = 3x² - 17x + 10

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

3) Soit x=1
A = 3x² - 17x + 10
= 3 - 17 + 10
A = -4

4) ( x-5 )( 3x-2 ) = 0
Donc x-5 = 0
x = 5
Ou 3x-2 = 0
3x = 2
x = 2/3