Final answer:
The quadratic function f(x) = x^2, after a vertical stretch by a factor of 2, is represented by g(x) = 2x^2. The correct answer is C. g(x) = 2x2.
Step-by-step explanation:
The question concerns the transformation of a quadratic function involving a vertical stretch. The original function given is f(x) = x2.
When we apply a vertical stretch by a factor of 2, we are essentially multiplying the entire function by 2.
Thus, the transformed function, represented by g(x), would be g(x) = 2x2.
This scaling affects the 'a' coefficient in the standard quadratic function y = ax2, which results in a steeper parabola. Therefore, the correct answer is C. g(x) = 2x2.