Answer:
1. Center: origin
Radius: 12 units
Equation: x² + y² = 144
2. Center: (2,6)
Radius: 9 units
Equation: (x - 2)² + (y - 6)² = 81
3. Center: (-7.2)
Radius: 15 units
Equation: | x + 7.2 | = 15
4. Center: (-4,-5)
Radius: 512 units
Equation: (x + 4)² + (y + 5)² = 262144
5. Center: (10.-8)
Radius: 3V3 units
Equation: (x - 10)² + (y + 8)² = 81V²
