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Rezolva sistemul
x+y+xy=5
(x+y)xy=6


Răspuns :

x+y+yx = 5

(x+y)xy = 6

s+p = 5

s•p = 6

S = 5

P = 6

t²-St+P = 0 => t²-5t+6 = 0

Delta = 25-24 = 1 => t1,2 = (5±1)/2

=> t1 = 2, t2 = 3

=> s = 2, p = 3 sau s = 3, p = 2

=> x+y = 2

=> xy = 3

t²-2t+3 = 0

Delta = 4-12 < 0 (nu avem soluții)

x+y = 3

xy = 2

t²-3t+2 = 0

Delta = 9-8 = 1

=> t1,2 = (3±1)/2

=> a = 1, b = 2 sau a = 2, b = 1.