Решите системы уравнений x/y =1/3 y/x=1/2 x^2 + y^2 = 50 x^2-y^2=21

1) 3x=y
   x^2+9x^2=50 x^2=5 x=sqrt(5) y=3sqrt(5)
                                     x=-sqrt(5) y=-3sqrt(5)
2) x=2y
     3y^2=21
y^2=7
y=sqrt(7) x=2sqrt(7)
y=-sqrt(7) x=-2sqrt(7)