X^2+y^2=5 x^4-y^4=15 решите систему уравнений

Х^2 = а; х^4 = а^2

y^2 = b; y^4 = b^2

a + b = 5

a^2 - b^2 = 15

a = 5 - b

a^2 = 25 - 10b + b^2

25 - 10b + b^2 - b^2 = 15

25 - 10b = 15

10b = 10

b = 1

a = 5 - 1 = 4

X^2 = a

X^2 = 4

X1 = 2; X2 = - 2

y^2 = b

y^2 = 1

y1 = 1; y2 = - 1

Ответ (2; 1) ; (- 2; - 1)