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Quadratic Functions (Basics)

🎯 Learning Goals

  • Understand the shape and meaning of the parabola y = ax²
  • Learn how the coefficient 'a' affects the width and direction of the graph

💡 Why Learn This?

Quadratic functions describe motions like a thrown ball's trajectory (parabola), car braking distances, and satellite dish shapes. They are fundamental in physics, engineering, and optimizing curves.

The Power of Squared: y = ax²

Unlike linear functions that grow at a steady rate, quadratic functions have a variable 'x' that is squared. This means as 'x' grows, 'y' grows much faster, creating a curved U-shape called a parabola.

Properties of the Parabola

  • It is symmetrical around the y-axis.
  • The lowest (or highest) point is called the vertex (for y = ax², it is at the origin 0,0).

⚠️ Common Pitfalls

A common mistake is forgetting that squaring a negative number results in a positive number. For example, (-3)² is 9, not -9. This is why the graph curves upwards on both the left and right sides (when a > 0).

Parabola Explorer

Adjust the value of 'a' to see how the parabola y = ax² changes its shape and direction.

y = 1

Coefficient 'a':1
Shape:Opens Up (U-Shape)

📝 Summary & Recap

  • The graph of y = ax² is a parabola passing through the origin.
  • If 'a' is positive, it opens upwards. If 'a' is negative, it opens downwards. A larger absolute value of 'a' makes the parabola narrower.

Quick Drill

Test your understanding of parabolas!

In the function y = ax², what happens to the graph if 'a' is a negative number (e.g., a = -2)?

🔍 Deep Dive (Optional)

Telescopes and satellite dishes use parabolic mirrors. Because of a mathematical property of the parabola, all incoming parallel rays of light or radio waves bounce off the curve and hit a single 'focal point', creating a strong signal!