Linear functions are an important topic in Year 9 math, and they have some special traits. Let's break them down:

1. Form: The basic equation for a linear function looks like this:

   [ y = mx + b ]

   Here:

   • m is the slope, which tells us how steep the line is.
   • b is the y-intercept, which is where the line crosses the y-axis.

2. Graph: When we draw linear functions on a graph, they make straight lines. For instance, the function

   [ y = 2x + 3 ]

   has a slope of 2 and crosses the y-axis at the point (0, 3). This means the line goes up sharply.

3. Slope: The slope shows us how steep the line is.

   • If m is a positive number, the line goes up as you move to the right.
   • If m is a negative number, the line goes down.

4. Domain and Range: For linear functions, the domain (the possible x-values) and range (the possible y-values) include all real numbers.

Understanding these features is really helpful! They allow us to analyze and solve real-life problems that involve linear relationships.