Odpowiedzi

  • Użytkownik Zadane
2013-07-14T17:21:38+02:00

l = r + 5

Pb = 50π

 

Pb = πrl
πrl = 50π       /:π
rl = 50
r(r + 5)  = 50

r² + 5r - 50 = 0

Δ  = 25 - 4 * 1 * (-50) = 25 + 200 = 225

√Δ = 15

r1 = (-5 - 15)/2 = -20/2 = -10 ∉ D

r2 = (-5 + 15)/2 = 10/2 = 5

 

r = 5

l = 5 + 5 = 10

 

odp.  r = 5  i  l = 10