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Year 8 - Maths

Negative rate of change from a graph

Graphical representations of linear equations

Unit Summary

In this unti we develop understanding of linear relationships and explore the key features of a linear equation such as the gradient, intercept and determining an equation from coordinate pairs.

Lesson Summary

You will learn to calculate the negative rate of change (gradient) from a graph.

Key Notes

  • Graphs can be described by looking at how quickly they fall.
  • The amount y decreases when x increases by one is the rate of change and is called the gradient.
  • The gradient will be negative if y decreases as the graph moves to the right.
  • The gradient can be found from any linear graph.
  • The gradient tells us important information about the relationship.

Vocabulary To Learn

  • Gradient: The gradient is a measure of how steep a line is.
  • Absolute value: The absolute value of a number is its distance from zero.
  • Parallel: Two lines are parallel if they are straight lines that are always the same (non-zero) distance apart.

Common Mistakes To Avoid

  • Pupils may think lines with gradients 2 and -2 are parallel.

3 Quick Questions (With Answers)

1. Solve this in steps: explain the method from this lesson and why each step matters.

Graphs can be described by looking at how quickly they fall. The amount y decreases when x increases by one is the rate of change and is called the gradient.

2. Use this key word in a maths sentence and explain it clearly. 'Gradient'

The gradient is a measure of how steep a line is. Use this word when showing your method, then check your final answer is reasonable.

3. Spot and fix this common maths mistake.

Mistake: Pupils may think lines with gradients 2 and -2 are parallel. Correction: Lines have to have the exact same gradient to be parallel. A line with a negative gradient will intersect a line with a positive gradient .

More Lessons In This Unit

Browse all guides in the Year 8 Maths guide library.