M3.9.4 For the adult
From a rule to a line
A rule gives a y number for every x number. Can I draw the rule as a picture?
What this chapter teaches
A rule such as y = 2x + 1 gives one y number for each x number. Each pair is a point, and the points lie on a straight line that goes on in both directions. A point that is not on the line does not fit the rule.
Three questions to ask
There is no one right wording. Listen for the idea.
- What is y when x is 4 in the rule y = 2x + 1?
- Why do the points of y = 2x + 1 lie on a straight line?
- How can you check that a point is on a line from its rule?
After the chapter, the learner can
- Make a table of values for y = 2x + 1
- Plot the points and join them with a straight line
What they copy into their notebook
A rule gives y for each x. Make a table, plot the points, and draw a straight line through them. The line goes on both ways. A point off the line breaks the rule.