M3.9.5 For the adult
Lines like x = 3 and y = −2
What does a line look like when x is always 3? And where do two lines meet?
What this chapter teaches
The rule x = 3 fixes the across number, so its line is upright. The rule y = −2 fixes the up number, so its line is flat. Two lines that are not parallel cross at one point, which fits both rules.
Three questions to ask
There is no one right wording. Listen for the idea.
- Is the line x = 5 upright or flat, and how do you know?
- Where do the lines x = 2 and y = 4 cross?
- How can you check that a crossing point is on both lines?
After the chapter, the learner can
- Draw lines like x = 3 and y = −2
- Find where two straight lines cross
What they copy into their notebook
The line x = 3 is vertical, through 3 on the x axis. The line y = −2 is horizontal, through −2 on the y axis. Two lines that are not parallel cross at one point. That point fits both rules.