Equations of Straight Line Graphs

August 23, 2016

Students learn how to plot and derive the equation of straight-line graphs in the form y = mx + c.  Learning progresses on from this to find the equation of parallel and perpendicular lines in the form ax + by +c = 0.

This unit takes place in Term 3 of Year 9 and is followed by graphical functions.

Equations of Straight Line Graphs Lessons
Algebra: Interactive Lessons
Plotting Straight Line Graphs
4 Part Lesson
Plotting Straight Line Graphs
Students learn how to plot straight line graphs in the form y = mx + c.
Algebra: Interactive Lessons
Equation of Straight Line Graphs
4 Part Lesson
Finding the Equation of Straight Line Graphs
Students learn how to find the equation of straight line graphs.
Algebra: Interactive Lessons
Gradient of Perpendicular Lines
4 Part Lesson
Gradient of Perpendicular Lines
Students learn how to work out the gradient of perpendicular straight line graphs.
Algebra: Interactive Lessons
Gradient of Parallel Lines
4 Part Lesson
Gradient of Parallel Lines
Students learn how to visualise straight line graphs with the same gradient.
Algebra: Interactive Lessons
Gradient of Straight Line Graphs
4 Part Lesson
Gradient of Straight Line Graphs
Students learn how to work out the gradient of straight-line graphs.
Algebra: Interactive Lessons
Plotting Straight Lines from Two Points
4 Part Lesson
Plotting Straight Lines from Two Points
Students learn how to plot the equation of a straight line using two points.
Additional Resources
Algebra: Interactive Lessons
Finding the equation of straight line graphs
Extended Learning
Finding the equation of straight line graphs
Additional practice finding the equation of straight-line graphs in the form y = mx + c.
Algebra: Interactive Lessons
Problem Solving - Straight Line Graphs
Problem Solving
Straight Line Graphs
Students are challenged to solve a range of problems involving straight line graphs.
Algebra: Interactive Lessons
Revising Perpendicular and Parallel Gradients
Revision
Perpendicular and Parallel Gradients
Revision lesson on finding the equation of parallel and perpendicular straight line graphs for exam students.
Algebra: Interactive Lessons
Revising Plotting Straight Line Graphs
Revision
Plotting Straight Line Graphs
Revision lesson on plotting straight line graphs in the form y = mx + c for exam students.
Algebra: Interactive Lessons
Revising the Equation of Straight Line Graphs
Revision
Equation of Straight Line Graphs
Revision lesson on finding the equation of straight line graphs for exam students.
Prerequisite Knowledge
  • Recognise and describe linear number sequences, including those involving fractions and decimals, and find the term-to-term rule.
  • Generate and describe linear number sequences
Success Criteria
  • Plot graphs of equations that correspond to straight-line graphs in the coordinate plane;
  • Use the form y = mx + c to identify parallel lines
  • Find the equation of the line through two given points, or through one point with a given gradient
  • Identify and interpret gradients and intercepts of linear functions graphically and algebraically
Key Concepts
  • Gradient is a measure of rate of vertical change divided by horizontal change.
  • Parallel lines have the same gradient
  • The intercept always has the x value equal zero.
Common Misconceptions
  • Students often confuse linear graphs to have the same notation as statistical graphs.
  • The gradient can be calculated from any two points along the graph. Not necessarily from the origin.
  • A linear function does not have to pass through the origin.
  • It is beneficial to create a table of results when plotting a linear function. The coordinate pairs arise from the x and y values.

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