Pouvez vous m’aider svp ? Merci d’avance

salut je pense que j'ai trouve la réponse:

1/ f(x)>d(x)

-500000/x + 35000 > -750x + 45000

-50000+35000x>-750x²+45000x

750x²-10000x-50000>0

2/ f(x)<d(x)

-500000/x + 35000 < -750x + 45000

-500000+35000x<-750x²+45000x

750x²-10000x-500000x<0

3/ 750x²-10000x-500000x<0

150x²-2000x-100000<0

15x²-200x-10000<0

3x²-40x-2000<0

et 750x²-10000x-500000x>0

150x²-2000x-100000>0

15x²-200x-10000>0

3x²-40x-2000>0

4/ a/ (x +20) (3x - 100)=3x²-100x+60x-2000=3x²-40x-2000

b/ f(x) > d(x)

750x²-10000x-50000>0

3x²-40x-2000>0

(x +20) (3x - 100)>0