Linear Equations with Fractions

Linear Equations with Fractions

Article Contents

  1. Equations with Fractions
  2. Unknown in the Numerator
  3. Unknown in the Denominator
  4. Clearing Fractions Early
  5. Examples

1. Equations with Fractions {#equations-with-fractions}

Fractions in equations can look scary, but the same balance principle applies.

Example with Fractions


2. Unknown in the Numerator {#unknown-in-the-numerator}

This is the standard case:

Formula: Multiply both sides by

Example

Solve:

Step 1: Multiply both sides by 4
Step 2: Calculate
Step 3: Check

3. Unknown in the Denominator {#unknown-in-the-denominator}

When is in the denominator, we need to be careful.

Example

Solve:

Step 1: Multiply both sides by
Step 2: Divide both sides by 2
Step 3: Check (remember: never divide by zero!)
Important: since we can't divide by zero!

4. Clearing Fractions Early {#clearing-fractions-early}

A helpful technique is to multiply the entire equation by the denominator to avoid working with fractions.

Example

Solve:

Method 1: Direct approach
Method 2: Clear fractions first

Both methods work! Method 2 is often cleaner.


5. Examples {#examples}

Example 1: Unknown in Numerator

Solve:

Step 1: Multiply both sides by 3
        2x = 24
Step 2: Divide both sides by 2
        x = 12

Check:


Example 2: Unknown in Denominator

Solve:

Step 1: Multiply both sides by x
        12 = 4x
Step 2: Divide both sides by 4
        x = 3

Check:


Example 3: Complex Fractions

Solve:

Step 1: Multiply both sides by 2
        x + 5 = 14
Step 2: Subtract 5 from both sides
        x = 9

Check:


Summary

SituationMethod
Multiply both sides by :
Multiply both sides by , then divide:
Multiply by , then divide by :

Interactive Exercises