Math 1 · Unit 5 · Lesson 3
Match It and Write It
Two directions. Read a graphed region and write its inequality from three clues: the boundary (m and b), the line style (dashed is strict, solid is inclusive), and the shaded side (above is greater, below is less). Then match an inequality to its graph by elimination with the same three clues, boundary first, without plugging in points except to check.
The big idea
A graphed region carries exactly three pieces of information, and they are the three parts of its inequality. The boundary line gives m and b, read the Unit 3 way. The line style gives the kind of sign: dashed is strict, solid is inclusive. The shaded side gives the direction: above is greater, below is less. Read the three clues and you have written the inequality. Run them the other way and you can pick the right graph out of several by elimination, boundary first, then style, then side, crossing out every graph that breaks a clue, which is the Unit 3 habit with two extra clues. Plug in a point only to double-check what the clues already decided.
The parts of this lesson
Each part is its own short page. Go in order, or pick the one you need.
Printables
One page with the three clues in both directions, the vertical and horizontal cases, and a worked read-and-write example. Plus a worksheet with grids and an answer key, and a short lesson plan.