Solving and Graphing Inequalities

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Mathematics · Algebra I
SP-ALG1-004  ·  Free to print and use in your classroom  ·  substituteplans.com
Page 2
Solving and Graphing Inequalities
Mathematics · Algebra I · Grades 8-9 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). Write the worked examples and the flip rule on
the board.
Technology
None. Calculators are optional for arithmetic only.
Student
independence
High. Students work alone, then compare with a partner.
Copies to make
One 2-page worksheet per student
Materials
Pencils, Worksheet, Whiteboard or chalkboard
Goal for today: Students will solve linear inequalities, apply the rule for reversing the inequality sign when
multiplying or dividing by a negative, and describe their graphs.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Write on the board: Solve an inequality like an equation, with ONE exception. If you multiply or divide both
sides by a NEGATIVE number, flip the sign.
☐ Write the example from the schedule on the board: −2x > 8, so x < −4.
☐ Keep the answer key on your desk. You do not need to solve anything yourself.
Say this to start
Good morning! Today you will solve inequalities. These look like equations, but instead of one answer they have a
whole range of answers. They work almost exactly like equations, with one special rule about negative numbers that is
written on the board. Work on your own, show your steps, and we will check answers near the end.


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Mathematics · Algebra I
SP-ALG1-004  ·  Free to print and use in your classroom  ·  substituteplans.com
Page 3
Run of show
Minutes
What you do
What students do
0–5
Take attendance the way the school requires. Hand out the
worksheet face down and ask students to wait.
Settle in and take out a pencil.
5–13
Read the board examples aloud. x + 3 > 7 gives x > 4.
Then −2x > 8: divide both sides by −2 and FLIP the sign,
so x < −4. Explain that on a number line, an open circle
means the number itself is not included (< or >) and a
closed circle means it is included (≤ or ≥). The arrow
points toward the numbers that work.
Follow along and copy the two examples.
13–28
Tell students to complete Part A (problems 1–6) and then
fill in the graph table. Walk the room and ask, “Did you
divide by a negative? Then did you flip the sign?”
Solve each inequality, then complete the
table about circles and arrows.
28–40
Tell students to do Part B (true/false 7–10) and Part C (word
problems 11–12). Partners may compare quietly.
Decide whether each statement is true or
false and write inequalities for the
situations.
40–46
Read the answers from the key. Students mark each right
or wrong and fix mistakes.
Check their work and correct errors in a
different color if possible.
46–50
Have students write the exit ticket sentence, then collect
all worksheets and stack them for the teacher.
Write one sentence. Hand in the worksheet.
If things go wrong
• If students ask why the sign flips, tell them to try it with numbers: 2 < 5, but −2 > −5 after multiplying both
by −1.
• If a student writes an answer like x = 5 for an inequality, remind them the answer should keep an inequality
sign.
• If a student cannot get started on a word problem, tell them to underline the phrase “at most” (≤) or “at
least” (≥).
• If the class is noisy, remind them this is individual practice time. Partners may whisper during Part B and C.
Early finishers
• Choose three numbers that make 2x − 5 ≥ 9 true and two numbers that make it false. Check each one.
• Write your own real-life situation that fits the inequality 3x ≤ 30.
Support and challenge
• Support: Have students complete problems 1, 2, 4 and 5, plus true/false 7 and 9, and circle the operation they
undo each time.
• Challenge: Ask students to solve −3(x − 2) ≥ 12 and explain how the sign changes.


SubstitutePlans.com
Mathematics · Algebra I
SP-ALG1-004  ·  Free to print and use in your classroom  ·  substituteplans.com
Page 4
Notes for the teacher (you fill this in)
Jot a few lines before you leave. A full Daily Sub Report is in the free Sub Survival Kit at SubstitutePlans.com.
How far the class got / what to pick up next:
Students who were especially helpful:
Anything the teacher should know: