1. draw a straight line whose equation is y = −x
Straight lines
GM4.1 Core Starter
On a grid:
draw a straight line whose equation is y = −x
draw a straight line parallel to y = −x, passing through (0, 1)
draw a third straight line, perpendicular to y = −x and passing through the point (0, 0)
draw a fourth straight line, also perpendicular to y = −x, but passing through the point (0, 1)
What is the difference between the equations of the first two lines and the last two lines?
Preamble
This short investigation recaps previous work on the equations of straight lines. The actual drawing of the four straight lines should be carried out quickly; pupils need to be able to draw such lines almost by recall. Encourage speculation about any possible patterns in the equations of the straight lines, then home in on the differences in the sign of x. Once this has been established, challenge the group to consider
y = −2x. What is the coefficient of x for a line perpendicular to this line?
Possible content
Drawing straight line graphs, plotting points, drawing perpendicular lines.
Resources
Squared paper for helping pupils draw coordinate grids.
Solution/Notes