Vertex Form of a Parabola
Vertex form y = a(x−h)² + k gives vertex (h,k), axis x = h, and direction from a. a > 0: opens up; a < 0: opens down. Converts to standard form by expanding.
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Vertex (h,k) is max if a<0, min if a>0. Axis of symmetry: x = h. Completing square converts standard → vertex.
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Why: Vertex form directly reveals the vertex and axis of symmetry. Used in optimization (vertex = max/min), projectile motion, and graphing parabolas.
How: Vertex (h,k) from the equation. Expand a(x−h)² + k to get standard form ax²+bx+c. Axis of symmetry x = h. Y-intercept: set x=0.
Run the calculator when you are ready.
Sample Examples
Input (y = a(x-h)² + k)
Results
Vertex
(0, 0)
Axis of symmetry: x = 0
Opens: up
Standard form: y = 1x² + -0x + 0
Y-intercept: (0, 0)
Zeros: 0
Visualization
For educational and informational purposes only. Verify with a qualified professional.
🧮 Fascinating Math Facts
y = a(x−h)² + k; vertex (h,k).
— Vertex Form
Axis of symmetry: x = h.
— Property
Key Takeaways
- Vertex form: y = a(x-h)² + k; vertex at (h,k)
- Axis of symmetry: x = h
- a > 0: opens up; a < 0: opens down
- Standard form: y = ax² + bx + c; b = -2ah, c = ah² + k
- Zeros from 0 = a(x-h)² + k → x = h ± √(-k/a)
Did You Know?
- Vertex form reveals transformations of y = x²
- Projectile motion: h(t) = -½gt² + v₀t + h₀
- Completing the square converts standard → vertex
- Optimal values at vertex (max/min)
- Used in optimization, physics, economics
- Parabola focus/directrix from vertex form
Understanding
Vertex form makes the vertex (h,k) and axis x=h explicit.
Expert Tips
- |a| > 1: narrower; 0 < |a| < 1: wider
- Y-intercept: set x=0 → y = ah² + k
- Zeros exist when k/a ≤ 0
- Completing square: h = -b/(2a), k = c - b²/(4a)
FAQ
A: Directly shows vertex, axis, direction.
A: Solve 0 = a(x-h)² + k; x = h ± √(-k/a).
A: When -k/a < 0 (a and k same sign).
A: Projectiles, profit max, optics.
A: Complete the square or use h=-b/(2a), k=c-b²/(4a).
A: Not quadratic; linear.
A: a>0 up, a<0 down.
How to Use
- Enter a, h, k for y = a(x-h)² + k
- Get vertex, axis, standard form, intercepts, zeros
- Visualize the parabola
Disclaimer
a ≠ 0 for quadratic. Zeros are real when -k/a ≥ 0.
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