The scope of Quadratic Graphs is very wide. For Sec 2, you are only expected to cover the following:
  • The effects of the constants a, b and c on the graph.
  • Recognise the graph given its equation
  • Know the line of symmetry of the graph
  • Able to derive the x-intercepts (by factorisation) and y-intercept given its equation
  • Sketch the graph showing the intercepts and turning point.

What is a Quadratic Graph?
Remember how to solve the equation quad_1.gif ?

Solution:
quad_2.gif

Well, a quadratic graph is simply the graph of quad_3.gif.
You can use either the Graphing Calculator or a graphing software (graphmatica, geogebra etc) to plot the graph.

From the graph, you should realise that the x-intercepts are actually the values of x when you solve the equation (above). Also, the y-intercept value is the constant in the equation.

Other observations about the graph: The graph is symmetrical about the y-axis. Hence, there is a line of symmetry, which is x = 2.5.

Basic Concepts:

The General Form of a Quadratic Curve is quad_4.gif , where a, b and c are constants.


Notes:

To recap the equation and how the values of a, b and c affect the graph, download these slides:

Worksheet for McDonald Sign:

Slides for Quadratic Curve Sketching:

Solutions to Quadratic Curve Sketching: