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.

Remember how to solve the equation ?

Solution:

Well, a quadratic graph is simply the graph of .
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 , 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: