x^2 + y^2 = 5
y = 2x
The second equation is solved for y, so substitute it in the first equation.
x^2 + (2x)^2 = 5
x^2 + 4x^2 = 5
5x^2 = 5
x^2 = 1
x^2 - 1 = 0
(x + 1)(x - 1) = 0
x = -1 or x = 1
Now substitute both values of x in the second equation and solve for y.
y = 2x
For x = -1
y = 2(-1)
y = -2
For x = 1
y = 2(1)
y = 2
Solution: (-1, -2), (1, 2)
