Recognise and plot lines y = kx and y = −kx

Home learning focus

In this lesson you will explore straight line graphs that pass through the origin.

This lesson includes:

  • one slideshow
  • two interactive activities

Created in partnership with Pearson


Work through these slides. You will need to draw some graphs and tables. Using squared paper will make it easier - there may be some in your school Maths workbook.

A table can be used to set out the values of x and y for the equation y = 3x. To work out the y coordinate, multiply the x coordinate by 3.

1 of 7

Lesson summary:

  • Graphs of the form y = kx or y = -kx are plotted as straight lines that pass through the origin (0, 0). k represents any number.
  • The greater the value of k, the steeper the graph.
  • Graphs of y = kx slope upwards. They have a positive gradient.
  • Graphs of y = -kx slope downwards. They have a negative gradient.


Activity 1

Recognise and plot lines y = kx and y = −kx

Have a go at the worksheet below from Pearson. Print it out or write your answers on paper.

Recognise and plot lines y = kx and y = −kx

Activity 2

Changes to a line

Try this activity from GeoGebra

Move the slider to change the gradient of the line in increments of 0.5, between -5 and +5 and note what changes and what stays the same.

There's more to learn

Have a look at these other resources around the BBC and the web.

KS3 Maths
BBC Bitesize Daily
Radio 1's Movie Mixtape: The chillest tracks
11-14 Maths
Coronavirus and your wellbeing
Bitesize Support