X²+y²=5; x-y=1 в фигурных скобках

X^2+y^2=5

x-y=1

x=y+1

(y+1) ^2+y^2=5

(y+1) (y+1) = y^2+y+y+1=y^2+2y+1

y^2+2y+1+y^2=5

2y^2+2y-4=0 |:2

y^2+y-2=0

D=1-4 * (-2) * 1=9

y_{1,2} = (-1+/-3) / 2

y_1 = 1; y_2 = - 2

x=1+1

x=2

x=-2+1

x=-1

(y=1; x=2) (y=-2; x = - 1)