Question: Give the function which reflects the graph of $y=x^3$ through the x-axis and stretches it vertically by a factor of 2.
1. **State the problem:** We need to find the function that results from reflecting the graph of $y=x^3$ through the x-axis and then stretching it vertically by a factor of 2.
2. **Reflection through the x-axis:** Reflecting a function $y=f(x)$ through the x-axis changes the sign of the output, so the reflected function is $y=-f(x)$.
3. **Vertical stretch by a factor of 2:** Stretching a function vertically by a factor of 2 multiplies the output by 2, so the stretched function is $y=2f(x)$.
4. **Apply reflection first:** Reflect $y=x^3$ through the x-axis:
$$y = -x^3$$
5. **Apply vertical stretch:** Stretch the reflected function by a factor of 2:
$$y = 2(-x^3) = -2x^3$$
6. **Final function:** The function after reflection and vertical stretch is:
$$y = -2x^3$$
This function reflects the original cubic graph through the x-axis and stretches it vertically by 2.