The solution to 4(x − 5)/3 + 2 = 14 is
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.
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.
What value for the constant, k, will result in no solution for the equation k(5x + 7) = 10x + 12?
When solved for x in terms of a, the solution to the equation 3x − 7 = ax + 5 is
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…