Step 1: Analyze the given 3D hollow geometry (Figure D). It consists of six triangular faces and nine equal edges, forming a symmetrical structure.
Step 2: Identify which given net diagrams (P, Q, R, S) can be folded along the dotted lines to form the described 3D shape.
- Option P: Contains six triangles arranged in a way that they can be folded into a symmetrical 3D figure.
- Option Q: Also consists of six triangles correctly placed for forming the shape.
- Option R: Maintains the same triangular face count and edge arrangement, making it valid.
- Option S: The triangular faces are not arranged correctly to form the required 3D structure.
Step 3: Since P, Q, and R can be folded into the required 3D shape, the correct answer is:
\[ \text{P, Q, and R} \] Thus, the correct answer is option C.
Let $ a_0, a_1, ..., a_{23} $ be real numbers such that $$ \left(1 + \frac{2}{5}x \right)^{23} = \sum_{i=0}^{23} a_i x^i $$ for every real number $ x $. Let $ a_r $ be the largest among the numbers $ a_j $ for $ 0 \leq j \leq 23 $. Then the value of $ r $ is ________.
Let $ y(x) $ be the solution of the differential equation $$ x^2 \frac{dy}{dx} + xy = x^2 + y^2, \quad x > \frac{1}{e}, $$ satisfying $ y(1) = 0 $. Then the value of $ 2 \cdot \frac{(y(e))^2}{y(e^2)} $ is ________.
The left and right compartments of a thermally isolated container of length $L$ are separated by a thermally conducting, movable piston of area $A$. The left and right compartments are filled with $\frac{3}{2}$ and 1 moles of an ideal gas, respectively. In the left compartment the piston is attached by a spring with spring constant $k$ and natural length $\frac{2L}{5}$. In thermodynamic equilibrium, the piston is at a distance $\frac{L}{2}$ from the left and right edges of the container as shown in the figure. Under the above conditions, if the pressure in the right compartment is $P = \frac{kL}{A} \alpha$, then the value of $\alpha$ is ____