Répondre :

(3x+12)*(2x+1)
=6x²+24x+3x+12
=6x²+27x+12
= ( 3x + 12 ) * ( 2x + 1 )
= 3x * 2x + 3x * 1 + 12 * 2x + 12 * 1
= 6x^2 + 3x + 24x + 12
= 6x^2 + 27x + 12