Répondre :
A = (6x+2)²
=36x²+24x+4
B = (7x-4)²
=49x²-56x+16
C = (2x+9)(2x-9)
= 4x²-18x+18x-81
=4x²-81
D = (3x-5)(x+2)+(3x+2)²
= 3x²+6x-5x-10+9x²+12x+4
=12x²+13x-6
=36x²+24x+4
B = (7x-4)²
=49x²-56x+16
C = (2x+9)(2x-9)
= 4x²-18x+18x-81
=4x²-81
D = (3x-5)(x+2)+(3x+2)²
= 3x²+6x-5x-10+9x²+12x+4
=12x²+13x-6