x+y=5 x²+y²=13 comment resoudre sa svp

y = 5 - x
X2 + (5 - x)2 = 13
x2 + 25 - 10 x + x2 = 13
2x2 -10x +12 =0
x2 - 5x + 6 = 0
x = 0.5 (5 ± √25-24 = 2.5 ± 0.5
Deux solutions :  x1 = 3 et x2 = 2.  
Et : y1 = 2  et y2 = 3