Solve: System of Equations

x^2+y^2=16
256x^2+25y^2=6400

I know the answers have radicals, but i can't figure this out
help please!

x^2 + y^2 = 16

y^2 = 16 - x^2

256*x^2 + 25*y^2 = 6400

256*x^2 + 25*(16 - x^2) - 6400 = 0

231*x^2 - 6000 = 0

231*x^2 = 6000

x^2 = 2000/77

x1 = sqrt(2000/77) = (20/77)*sqrt(385), x2 = - sqrt(2000/77) = - (20/77)*sqrt(385)

x^2 + y^2 = 16

y^2 = 16 - 2000/77

y^2 = - 768/77

y1 = i*sqrt(768/77) =(16/77)*i*sqrt(231) , y2 = - i*sqrt(768/77) = - (16/77)*i*sqrt(231)

((20/77)*sqrt(385); (16/77)*i*sqrt(231)),
((20/77)*sqrt(385); - (16/77)*i*sqrt(231)),
( - (20/77)*sqrt(385); (16/77)*i*sqrt(231))
( - (20/77)*sqrt(385); - (16/77)*i*sqrt(231))