Répondre :

"le coup du 1"
A=(3x+1)(x-2)+3x+1
=(3x+1)(x-2)+1*(3x+1)
=(3x+1)(x-2+1)
=(3x+1)(x-1)

"le coup du 1"
A=(3x+1)(x-2)-3x-1
=(3x+1)(x-2)+(-1)*(3x+1)
=(3x+1)(x-2-1)
=(3x+1)(x-3)

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