Công thức toán học nhiều màu trên bảng đen

Frequently used math formulas for high school entrance exams neatly handwritten in chalk on a dark green chalkboard. The formulas are color-coded in [white, yellow, cyan, and light pink] chalk, clearly organized by topic into distinct sections with neat handwriting, geometric diagrams, and clean layout that is easy to understand at a glance. Frontal flat-lay perspective, soft ambient classroom lighting.