Sagot :
Bsr
D = (-7x+6)(5-x²)
D = -7x×5-7x×(-x²)+6×5-6x²
D = -35x-7x×(-x²)+6×5-6x²
D = -35x+7x×x²+6×5-6x²
D = -35x+7x³+6×5-6x²
D = -35x+7x³+30-6x²
Voilà !
Bsr
D = (-7x+6)(5-x²)
D = -7x×5-7x×(-x²)+6×5-6x²
D = -35x-7x×(-x²)+6×5-6x²
D = -35x+7x×x²+6×5-6x²
D = -35x+7x³+6×5-6x²
D = -35x+7x³+30-6x²
Voilà !