Bonjour,
55)
1) Aj = pi (x/2)²*2/4 = pi*(x²/4)*2/4 = pi*x²/8
Av = (4*x)-pi*x²/8 = 4x-pi*x²/8
Av >= Aj <--> 4x-pix²/8 >= pi*x²/8 <--> 2*pi*x²/8 <= 4x <--> pi*x² <= 16x
2) pi*x² <= 16x <--> pi*x²-16x <= 0 <--> x(pi*x-16) <= 0
x -inf 0 16/pi +inf
x - 0 + +
pi*x-16 - - 0 +
x(pi*x-16) + 0 - 0 +
Ensemble des solutions S = [0 ; 16/pi]
89)
Je ne vois pas quelle est la question mais je vais te calculer Vc et Vp
Vc = volume du cube =
Vc = x^3
Vp = volume du pavé = (x+20)(x+20)(x-20) =
Vp = (x²+20x+20x+400)(x+20) =
Vp = (x²+40x+400)(x+20) =
Vp = x^3+20x²+40x²+800x+400x+8000=
Vp = x^3+60x²+1200x+8000
J'espère que tu as compris, si il y a des compléments écrits moi on continuera en chat.
a+
