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Equations & inequalities / LESSON 05

Linear equations, systems and boundaries · CLEP College Algebra

10 min + practice · Original foundation lesson

Linear equations and inequalities can be solved by reversible operations, but an inequality changes direction when multiplied or divided by a negative number.

A reliable method

Collect variable terms and constants separately. For a system, use substitution or elimination and verify the resulting ordered pair in both original equations.

The common trap

Moving a term is shorthand for applying an operation to both sides. That shorthand can hide a sign error if you do not know which operation it represents.

Check and transfer

Represent the final answer in the form requested. A boundary value, a solution interval and one coordinate of a system are related but are not interchangeable outputs.

Worked comparison: identify the structure

Solve (2x−3)/4=5 by clearing the denominator: 2x−3=20, then x=23/2. Adding three before multiplying only the right side by four would change the original equation. Substitute back to check that the original fraction equals five.

Transfer and explain

For −2x+7<1, subtract seven to get −2x<−6, then divide to get x>3. The boundary number and the direction are separate parts of the solution; test x=4 in the original inequality.

WORKED EXAMPLE

Solve (2x − 2)/3 = 5. What is x?

  1. Multiply both sides by 3.
  2. Add the subtracted constant before dividing by the coefficient of x.
  3. The requested value is 17/2. Substitute or reverse the operation to check this result.
Answer: 17/2
Compare the other answer choices
17

Stop before dividing the x coefficient two.

7/2

Omit multiplication of the right side by three.

17/6

Divide by three again after clearing the fraction.

Try it, then explain it.

Complete a short set without looking at the example. After each answer, explain which operation preserved the relationship and why the result makes sense.

Practice this skill

Sources & authorship

Original Slope explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.

CLEP College Algebra exam overviewSiyavula Grade 10 foundation reference