Double Integrals
1. **Problem a)**: Evaluate or describe the region of integration for
$$\int_0^4 \int_{\frac{4-y}{7}}^1 f(x,y) \, dx \, dy.$$
- Here, $y$ ranges from 0 to 4.
- For each fixed $y$, $x$ ranges from $\frac{4-y}{7}$ to 1.
2. **Problem б)**: Evaluate or describe the region of integration for
$$\int_{-\sqrt{2}}^{-1} \int_{-2 - x^2}^0 f(x,y) \, dy \, dx + \int_{-1}^0 \int_x^0 f(x,y) \, dy \, dx.$$
- The first integral covers $x$ from $-\sqrt{2}$ to $-1$, and for each $x$, $y$ ranges from $-2 - x^2$ to 0.
- The second integral covers $x$ from $-1$ to 0, and for each $x$, $y$ ranges from $x$ to 0.
3. **Explanation of regions:**
- For a), the region is bounded below by the curve $x = \frac{4-y}{7}$ and above by $x=1$, with $y$ between 0 and 4.
- For б), the region is split into two parts:
- Part 1: $x \in [-\sqrt{2}, -1]$, $y \in [-2 - x^2, 0]$ (a curved lower boundary).
- Part 2: $x \in [-1, 0]$, $y \in [x, 0]$ (a linear lower boundary).
4. **Summary:**
- These integrals define integration over specific regions in the $xy$-plane.
- Without a specific function $f(x,y)$, the integrals represent the total integral over these regions.
Final answer: The integrals describe the integration of $f(x,y)$ over the specified regions in the $xy$-plane as detailed above.