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Linear Equations in One Variable

Introduction

Linear equations in one variable form the foundation of algebra. These are equations that contain only one unknown (usually denoted as x) and the highest power of the variable is 1.

This pattern is important because it helps in developing basic problem-solving skills and logical reasoning - essential for all higher-level math topics.

Pattern: Linear Equations in One Variable

Pattern

The key concept: Simplify both sides and isolate the variable to find its value.

The general form of a linear equation in one variable is:
ax + b = c

To solve, bring all variable terms to one side and constants to the other side, then divide by the coefficient of x.

Step-by-Step Example

Question

Solve for x: 3x + 5 = 20

Solution

  1. Step 1: Write the given equation

    3x + 5 = 20.
  2. Step 2: Move the constant to the other side

    Subtract 5 from both sides:
    ⇒ 3x = 20 - 5 = 15.
  3. Step 3: Isolate x by dividing

    Divide both sides by 3:
    ⇒ x = 15 ÷ 3 = 5.
  4. Final Answer:

    5
  5. Quick Check:

    Substitute x = 5 into the original equation: 3(5) + 5 = 15 + 5 = 20 ✅

Quick Variations

1. Variables on both sides → e.g., 2x + 3 = x + 7

2. Fractional coefficients → e.g., (x/2) + 3 = 5

3. Negative or decimal coefficients → e.g., -0.5x + 4 = 2

Trick to Always Use

  • Step 1: Collect all variable terms on one side.
  • Step 2: Move constants to the other side.
  • Step 3: Simplify and divide to get the final answer.

Summary

Summary

In the Linear Equations in One Variable pattern:

  • Keep the equation balanced - whatever you do to one side, do to the other.
  • Always simplify step by step.
  • Substitute back to verify your solution quickly.

Practice

(1/5)
1. Solve for x: 5x + 7 = 22
easy
A. 3
B. 4
C. 5
D. 6

Solution

  1. Step 1: Identify the equation

    5x + 7 = 22.
  2. Step 2: Move the constant to the other side

    5x = 22 - 7 = 15.
  3. Step 3: Divide by the coefficient of x

    x = 15 ÷ 5 = 3.
  4. Final Answer:

    3 → Option A.
  5. Quick Check:

    5(3) + 7 = 15 + 7 = 22 ✅
Hint: Subtract the constant first, then divide by the coefficient.
Common Mistakes: Forgetting to subtract the constant before dividing; arithmetic errors.
2. Solve for x: 4x - 9 = 7
easy
A. 2
B. 3
C. 4
D. 5

Solution

  1. Step 1: Identify the equation

    4x - 9 = 7.
  2. Step 2: Add the constant to the other side

    4x = 7 + 9 = 16.
  3. Step 3: Divide to isolate x

    x = 16 ÷ 4 = 4.
  4. Final Answer:

    4 → Option C.
  5. Quick Check:

    4(4) - 9 = 16 - 9 = 7 ✅
Hint: Move constants across the equals sign (change sign), then divide.
Common Mistakes: Changing signs incorrectly when moving terms; simple division mistakes.
3. Solve for x: 2x + 3 = 11
easy
A. 2
B. 3
C. 5
D. 4

Solution

  1. Step 1: Identify the equation

    2x + 3 = 11.
  2. Step 2: Subtract the constant

    2x = 11 - 3 = 8.
  3. Step 3: Divide to isolate x

    x = 8 ÷ 2 = 4.
  4. Final Answer:

    4 → Option D.
  5. Quick Check:

    2(4) + 3 = 8 + 3 = 11 ✅
Hint: Remove constants first, then divide by the coefficient of x.
Common Mistakes: Dividing before subtracting the constant; mixing up arithmetic.
4. Solve for x: 7x - 4 = 24
medium
A. 3
B. 4
C. 5
D. 6

Solution

  1. Step 1: Identify the equation

    7x - 4 = 24.
  2. Step 2: Add the constant to the other side

    7x = 24 + 4 = 28.
  3. Step 3: Divide to isolate x

    x = 28 ÷ 7 = 4.
  4. Final Answer:

    4 → Option B.
  5. Quick Check:

    7(4) - 4 = 28 - 4 = 24 ✅
Hint: Always isolate the term with x first, then divide.
Common Mistakes: Arithmetic slip when adding or dividing; misreading the equation.
5. Solve for x: 9x + 15 = 42
medium
A. 3
B. 2
C. 4
D. 5

Solution

  1. Step 1: Identify the equation

    9x + 15 = 42.
  2. Step 2: Subtract the constant

    9x = 42 - 15 = 27.
  3. Step 3: Divide to isolate x

    x = 27 ÷ 9 = 3.
  4. Final Answer:

    3 → Option A.
  5. Quick Check:

    9(3) + 15 = 27 + 15 = 42 ✅
Hint: Simplify constants first; then divide by the coefficient.
Common Mistakes: Not simplifying the constant term correctly before division.

Mock Test

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