Question

Resolva o sistema :
x² + y² = 20
x + y = 6

Answer 1

   x²+y²= 20
   x +y = 6 ------> x=6-y

  (6-y)² + y² = 20
  36 - 12y + y² +y²= 20
  36 - 12y +2y² - 20 = 0
  2y² - 12y + 16= 0
   y² - 6y + 8 = 0 
Δ = 36 - 32 = 4
√Δ = √4 = 2

y' = (6+2)/2= 4
y"= (6-2)/2= 2

x+y=6 
para y = 4 ---> x= 6-4=2
para y = 2 ---> x= 6-2= 4