Coucou,
exo 1:
A= (2x+3) ²
A= (2x) ²+2×2x×3+3²
A= 4x²+12x+9
B=(5x-4)²
B= (5x)²-2×5x×4+4²
B= 25x²-40x+16
C=(9x-4) (9x+4)
C= (9x)²-4²
C= 81x²-16
D=(2x-3)(5x+3) +(9x-4)(3x+2)
D= 2x×5x+2x×3-3×5x-3×3+9x×3x+9x×2-4×3x-4×2
D= 10x²+6x-15x-9+27x²+18x-12x-8
D= 37x²-3x-17
E=(2x-3)(5x+3) -(9x-4) (3x+2)
E= 2x×5x+2x×3-3×5x-3×3-9x×3x-9x×2-4×3x-4×2
E= 10x²+6x-15x-9-27x²-18x-12x-8
E= -17x²-39x-17
voilà ☺