Bonsoir,
C=(x-7)(x+9)
= x²+9x -7x -63
= x² +2x -63
B=(x+3)(2x+4)
= 2x² +4x +6x +12
= 2x² +10x +12
D=(x-3)(4-4)
= 4x -4x -12 +12
= 0
E=(3x+4)(5x-7)
= 15x² -21x +20x -28
= 15x² -x -28
F=(-2x+8)(4-x)
= -8x +2x² +32-8x
= 2x² -16x + 32
C=(x-7)(x+9)
=(x×x)+(x×9)-(7×x)-(7×9)
=x^2+9x-7x-63
=x^2+2x-63
B=(x+3)(2x+4)
=(x×2x)+(x×4)+(3×2x)+(3×4)
=2x^2+4x+6x+12
=2x^2+10x+12
D=(x-3)(4-4)
=(x-3)(0)
=0
E=(3x+4)(5x-7)
=(3x×5x)-(3x×7)+(4×5x)-(4×7)
=15x^2-21x+20x-28
=15x^2-x-28
F=(-2x+8)(4-x)
=-(2x×4)+(2x×x)+(8×4)-(8×x)
=-8x+2x^2+32-8x
=2x^2-16x+32