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Linear Equations in One Variable

Introduction

Linear equations in one variable algebra की foundation बनाते हैं। ये ऐसे equations होते हैं जिनमें सिर्फ एक unknown होता है (आमतौर पर x) और variable की highest power 1 होती है।

यह pattern इसलिए ज़रूरी है क्योंकि यह basic problem-solving और logical reasoning skills को strong बनाता है - जो आगे के सभी higher-level math topics के लिए जरूरी हैं।

Pattern: Linear Equations in One Variable

Pattern

Key concept: दोनों sides को simplify करके variable को isolate करें और उसका value निकालें।

One-variable linear equation का general form होता है:
ax + b = c

Solve करने के लिए variable वाले terms को एक side पर और constants को दूसरी side पर ले जाएँ, फिर x के coefficient से divide करें।

Step-by-Step Example

Question

x का मान निकालें: 3x + 5 = 20

Solution

  1. Step 1: Given equation लिखें

    3x + 5 = 20.
  2. Step 2: Constant को दूसरी side ले जाएँ

    दोनों sides से 5 subtract करें:
    ⇒ 3x = 20 - 5 = 15.
  3. Step 3: Divide करके x isolate करें

    दोनों sides को 3 से divide करें:
    ⇒ x = 15 ÷ 3 = 5.
  4. Final Answer:

    5
  5. Quick Check:

    x = 5 put करने पर: 3(5) + 5 = 15 + 5 = 20 ✅

Quick Variations

1. Variables दोनों sides पर हों → जैसे 2x + 3 = x + 7

2. Fractional coefficients → जैसे (x/2) + 3 = 5

3. Negative या decimal coefficients → जैसे -0.5x + 4 = 2

Trick to Always Use

  • Step 1: सभी variable terms को एक side पर collect करें।
  • Step 2: Constants को दूसरी side पर ले जाएँ।
  • Step 3: Simplify करके divide करें ताकि final answer मिले।

Summary

Summary

Linear Equations in One Variable pattern में:

  • Equation को balanced रखें - एक side पर जो करें, वही दूसरी side पर भी करें।
  • हमेशा step-by-step simplify करें।
  • Solution verify करने के लिए वापस substitute करना न भूलें।

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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