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MAT 105 · Unit 1 ALEKS · objective 1.2

Inverse Operations and Checking

Use inverse operations on both sides of an equation and verify the result in the original equation.

Standalone concept package
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Build the concept from the beginning

Starting point

No prior equation-solving skill is assumed. Arithmetic operations, variables, equality, and every new algebra decision are explained on this page.

Learning target

Use inverse operations on both sides of an equation and verify the result in the original equation.

Evidence of mastery

Construct the reasoning path, solve at least 4 of 5 mastery problems, and revise an unfamiliar explanation.

Essential terms

equation
A statement that two mathematical expressions have the same value.
solution
A value that makes an equation true when substituted for the variable.
inverse operation
An operation that reverses another operation, such as subtraction reversing addition.
coefficient
A numerical factor multiplying a variable.
Look first, then name the mathematics

Build the visual meaning

Two equal panels receive the same subtraction and division, preserving balance while x is isolated.
How to read this visual: The paired-operation visual shows an operation being removed from both sides while the equation remains balanced.
  • Same operation
  • Both sides
  • Preserve equality
  • Isolate x
  • Check
Read the complete visual relationship as text
  • Same operation
  • Both sides
  • Preserve equality
  • Isolate x
  • Check by substitution
Definition in plain language

Inverse operations undo one another. Applying the same valid operation to both sides preserves equality while removing an operation from the variable.

Why this matters

This is the logic beneath every linear-solving step, including steps people sometimes describe informally as moving a term.

Reasoning path

See the method as a sequence

Move from left to right. Each decision prepares the next one; on a phone, follow the numbered cards from top to bottom.

Identify the outermost operation acting on the variable.
Choose its inverse operation.
Apply that operation to both complete sides.
Substitute the result into the original equation to check.

The same method in words

  1. Identify the outermost operation acting on the variable.
  2. Choose its inverse operation.
  3. Apply that operation to both complete sides.
  4. Substitute the result into the original equation to check.
Interactive decision model

Build the reasoning, one decision at a time

Choose the equality-preserving path for x/3 + 4 = 9.

Choose this step, then check the construction.
Choose this step, then check the construction.
Choose this step, then check the construction.

The reasoning path changes as each decision is selected.

Model before practice

Three fully explained examples

Every example identifies the goal, explains the next move, carries out the algebra, and checks or interprets the result.

Solve x + 7 = 19

Name the goalIsolate x while keeping both sides equal.
Choose the next moveSubtract 7 from both sides because subtraction undoes addition.
Carry out the mathematicsx + 7 − 7 = 19 − 7, so x = 12.
Check and interpretCheck: 12 + 7 = 19. The original equation is true.

Solve 5x = 35

Name the goalThe coefficient 5 multiplies x.
Choose the next moveDivide both sides by 5, the inverse of multiplying by 5.
Carry out the mathematics5x/5 = 35/5, so x = 7.
Check and interpretCheck: 5(7) = 35, so the solution is verified.

Solve x/4 = −3

Name the goalDivision by 4 is the operation acting on x.
Choose the next moveMultiply both sides by 4.
Carry out the mathematics4(x/4) = 4(−3), so x = −12.
Check and interpretCheck: −12/4 = −3. The sign and value are correct.

Practice with decreasing support

Guided practice

Practice immediately after the model

Predict first. Then use the visual relationship and reasoned feedback to check two decisions.

1. Which operation undoes adding 8?

2. Which operation undoes multiplying by 5?

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Partially completed problem

Finish the missing step

A prompt supplies part of the reasoning. Predict the missing mathematical move before choices appear.

1. Why must the same operation be performed on both sides?

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Independent practice

Six problems for repetition

Solve all six. Use the specific feedback to revise a method or sign error.

1. After solving x + 6 = 14 as x = 8, what is the best check?

2. What is the inverse of subtracting 3?

3. What is the inverse of dividing by 4?

4. Which step preserves 2x + 3 = 11?

5. If a check gives 12 = 12, what does that show?

6. If a check gives 7 = 10, what does that show?

Not completed yet.

Mastery and transfer

Mastery check

Demonstrate understanding

Attempt all five. At least four correct answers are required for mastery.

1. Which is a legal equality-preserving step from x/3 = 5?

2. Why is checking in the original equation stronger than checking only the final line?

3. What property justifies adding the same number to both sides?

4. What property justifies dividing both sides by the same nonzero number?

5. Which habit best prevents sign errors?

Not completed yet.
Unfamiliar transfer

Explain, compare, and revise

Explain why performing an operation on only one side usually changes the solution set.

Write a first attempt before opening the self-check.

The record reveals exact answers and model reasoning only after the corresponding attempt or self-check has occurred.