Which of the following functions' graphs are stretched horizontally by a factor of 2 when compared to the parent function f(x) = x^2? note that there may be other transformations as well, so the question is whether or not a particular transformation of the parent includes a horizontal stretch by a factor of 2.

g(x) = [(1/2)x]^2

g(x) = 2x^2

g(x) = (x/2)^2

g(x) = x^2 - 2

g(x) = 2x^2 + 17

g(x) = (2x)^2

g(x) = (1/2)x^2 + 17

g(x) = x^2 + 2

g(x) = (1/2)x^2