3. Дано: ABCDA₁B₁C₁D₁ – куб, D (2; 2; 0). 3. A (2; –2; 0), B (–2; –2; 0), C (–2; 2; 0), D (2; 2; 0), A₁ (2; –2; 4), B₁ (–2; –2; 4), C₁ (–2; 2; 4), D₁ (2; 2; 4).