Quadratic Function: y = ax² + bx + c

Graph: Parabola (U-shaped curve)

Vertex: Found by completing the square

Example 1: y = x² + 4x + 1 → complete square: (x + 2)² - 3 → vertex: (-2,-3)

Example 2: y = 2x² - 4x + 3 → complete square: 2(x - 1)² + 1 → vertex: (1,1)