Standard Form of a Quadratic Function: The form is a, b, and c are constants.
Parabola: The graph of a quadratic function in standard form is a parabola, a U-shaped curve.
Vertex: The minimum or maximum point of the parabola, which is a critical point for graphing.
Axis of Symmetry: A vertical line that passes through the vertex, dividing the parabola into two mirror-image halves. Its equation is derived from the coefficients of the standard form.
Y-intercept: The point where the parabola intersects the y-axis, which can be directly obtained from the standard form.
2. Key Concepts
Role of a:
Determines the direction the parabola opens: If $a > 0$ , the parabola opens upward (with a minimum vertex); if Affects the width of the parabola: Larger Axis of Symmetry: Calculated using the formula Vertex Calculation: The x-coordinate of the vertex is given by the axis of symmetry (Y-intercept: Occurs at Symmetric Points: For any point
3. Examples
Simple: Graph
Step 1: Identify coefficients: Step 2: Find axis of symmetry: Step 3: Calculate vertex: Substitute Step 4: Find y-intercept: Step 5: Find symmetric point of y-intercept: The axis of symmetry is Step 6: Plot points $a > 0$ ).
Key Features: Vertex
Step 1: Identify coefficients: Step 2: Find axis of symmetry: Step 3: Calculate vertex: Substitute Step 4: Find y-intercept: Step 5: Find symmetric point of y-intercept: Symmetric to Step 6: Plot points Key Features: Vertex
Step 1: Identify coefficients: Step 2: Find axis of symmetry: Step 3: Calculate vertex: Substitute Step 4: Find y-intercept: Step 5: Find symmetric point of y-intercept: Symmetric to Step 6: Choose an additional point (e.g., Step 7: Plot all points and connect them to form a narrow parabola opening upward (since $a = 2 > 0$ ).
Key Features: Vertex
4. Problem-Solving Techniques
Identify Coefficients: Extract a, b, and c from the standard form Calculate Axis of Symmetry: Use the formula Determine the Vertex: Substitute the x-coordinate of the axis of symmetry into the function to find the y-coordinate, giving the vertex Find the Y-intercept: Use Locate Symmetric Points: For any point Plot and Connect Points: Plot the vertex, y-intercept, symmetric points, and any additional points (if needed), then draw a smooth curve through them to form the parabola.
Analyze Key Features: After graphing, confirm the direction of opening, domain, range, and minimum/maximum value based on a and the vertex.