Finding the Slope of a Horizontal Line

Q1. Find the slope of the line $y = -9$.

Background

Topic: Slope of a Line

This question is testing your understanding of how to identify the slope of a line given its equation, especially when the equation is in the form $y = c$, where $c$ is a constant.

Key Terms and Formulas

• Slope (m): The measure of the steepness of a line, often represented as $m$ in the equation $y = mx + b$.

• Horizontal Line: A line with an equation of the form $y = c$ (where $c$ is a constant) is a horizontal line.

• General Slope-Intercept Form:

  $y = mx + b$

Step-by-Step Guidance

1. Recognize that the equation $y = -9$ is in the form $y = c$, which means it is a horizontal line passing through $y = -9$ on the y-axis.

2. Recall that the slope of any horizontal line is always the same, regardless of where it crosses the y-axis.

3. Compare the given equation to the slope-intercept form $y = mx + b$. Notice that there is no $x$ term in $y = -9$.

4. Think about what value of $m$ (the slope) would make $mx$ disappear from the equation.

Try solving on your own before revealing the answer!