Bonjour,
A = 2x(x + 3)
= 2x² +6
B = -7y²(-5- 2y²)
= 35y² + 14y^4
C = (x + 5)(x + 1)
= x² + x+5x +5
= x² + 6x + 5
D = (2x - 5) (x + 4)
= 2x² +8x -5x -2
= 2x² +3x -2
E = 3x²+2x+3-(4x²+5x+9)
= 3x²+2x+3-4x²-5x-9
= -x² -3x -6
F = (x + 4)(x - 6) + (-1 + x)(x - 7)
= x² -6x +4x -24 -x +7 +x² -7x
= 2x² -10x -17
G = -3(a² + 2) -(a -3)(2a + 7)
= -3a² -6 -( 2a² +7a -6a -21)
== -3a² -6 - 2a² -7a +6a +21
= -5a² -a +15
H = 4 -(2x + 1)²
= 4 - 4x² -4x -1
= -4x² -4x +3