Monotony Cube Root
1. **State the problem:** We are given the function $$y=\sqrt[3]{27-8x^3}$$ and asked to discuss its monotony, i.e., where it is increasing or decreasing.
2. **Recall the formula and rules:** To analyze monotony, we find the derivative $$y'$$ and determine where $$y' > 0$$ (increasing) or $$y' < 0$$ (decreasing).
3. **Rewrite the function:** $$y = (27 - 8x^3)^{\frac{1}{3}}$$
4. **Find the derivative using the chain rule:**
$$y' = \frac{1}{3}(27 - 8x^3)^{-\frac{2}{3}} \cdot (-24x^2) = -8x^2 (27 - 8x^3)^{-\frac{2}{3}}$$
5. **Analyze the sign of $$y'$$:**
- The term $$x^2 \geq 0$$ for all real $$x$$.
- The term $$(27 - 8x^3)^{-\frac{2}{3}} > 0$$ for all $$x$$ where the expression inside the root is defined (since even root of a real number cubed is defined and the power is negative but even).
- The negative sign in front makes $$y' \leq 0$$ for all $$x$$.
6. **Conclusion:**
- $$y' = 0$$ only at $$x=0$$.
- For $$x \neq 0$$, $$y' < 0$$, so the function is strictly decreasing everywhere except possibly flat at $$x=0$$.
**Final answer:** The function $$y=\sqrt[3]{27-8x^3}$$ is monotonically decreasing on its entire domain.