What are the solutions to the equations?

X^2 + y^2 = 5

y=2x

X^2 + (2x) ^2=5

x^2+4x^2-5=0

5x^2-5=0

5 (x^2-1) = 0

x^2-1=0

(x + square root of 1) * (x - square root of 1) = 0

x = square root of 1 or x = - square root of 1

then plug into y=2x

y = 2 times square root of 1 or y = - 2 times square root of 1