Unit 4 · Solving Linear Equations & Inequalities

Solving Linear Equations

Use inverse operations, keeping the equation balanced. If variables cancel, interpret the remaining true or false statement.

NY-8.EE.7AI-A.REI.3AI-A.CED.1

Notes

Balance, don't hop

Whatever you do to one side, do to the other. Distribute first, combine like terms, collect variable terms, then isolate.

Special cases

If you obtain 0 = 0, every real number works (identity). If you obtain 0 = 5, there is no solution. Algebra I also solves ax + b = c with letter coefficients.

Vocabulary

identity

An equation true for all values of the variable.

Example: 2(x + 3) = 2x + 6 is an identity.

no solution

An equation that is never true.

Example: x + 1 = x + 4 has no solution.

Worked examples

Try the prompt first. The steps stay folded until you ask to see them.

Variables on both sides

Solve 5x − 4 = 2x + 11.

Common errors

Watch for

Only moving the variable and forgetting the sign

Subtracting 2x is not the same as dropping it.

Fix: Write the inverse operation on both sides.

Explore with an applet

Guided practice

Submit each answer to check it. The key is not shown until you do.

Question 1 of 3Both examsAI-A.REI.3Algebra I Regents · June 2024 · Q6Non-calculatorproficient

The solution to 4(x − 5)/3 + 2 = 14 is

Answer choices
Choose or type an answer first. The key stays hidden until you do.
Question 2 of 3Both examsNY-8.EE.7Grade 8 Mathematics · Spring 2022 · Q39Non-calculatoradvanced

What value for the constant, k, will result in no solution for the equation k(5x + 7) = 10x + 12?

Answer choices
Choose or type an answer first. The key stays hidden until you do.
Question 3 of 3Algebra I RegentsAI-A.REI.3Algebra I Regents · June 2024 · Q22Non-calculatoradvanced

When solved for x in terms of a, the solution to the equation 3x − 7 = ax + 5 is

Answer choices
Choose or type an answer first. The key stays hidden until you do.

Intervention

Use the balance applet. Do one operation at a time and check.

Enrichment

Solve a literal equation for a specified variable, such as 2ℓ + 2w = P for w.

Explain your reasoning

Sentence starters · Notice and Wonder · Three Reads · Think-Pair-Share · Compare and Connect · Math Talk · Stronger and Clearer Each Time

  • I did the same operation on both sides because…
  • The variables canceled, so I looked at the remaining statement…