Factoring Formulas: Perfect Square, Difference of Squares, and Difference & Sum of Cubes, Cheat Sheet of Mathematics

Formulas and examples for factoring perfect squares, differences of squares, and differences and sums of cubes. It includes step-by-step solutions for various examples.

Typology: Cheat Sheet

2021/2022

Uploaded on 02/07/2022

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5.6 Special Factoring Formulas
A. Perfect Square Factoring
1. Perfect Square Factoring Formulas:
๎˜€๎˜ ๎˜‚ ๎˜ƒ๎˜€ ๎˜„ ๎˜‚ ๎˜„๎˜ ๎˜… ๎˜†๎˜€ ๎˜‚ ๎˜„ ๎˜‡๎˜
and
๎˜€๎˜ ๎˜ˆ ๎˜ƒ ๎˜€ ๎˜„ ๎˜‚ ๎˜„๎˜ ๎˜… ๎˜†๎˜€ ๎˜ˆ ๎˜„๎˜‡ ๎˜
2. To use: if the first and last terms of a trinomial are squares, try writing a perfect square;
then use the square formula to see if you are correct.
3. Examples:
Example 1: Factor
๎˜‰๎˜Š
๎˜ ๎˜‚ ๎˜‹ ๎˜ƒ
๎˜Š
๎˜‚ ๎˜Œ
.
Solution
Since
๎˜‰๎˜Š
๎˜๎˜… ๎˜†๎˜ƒ
๎˜Š
๎˜‡๎˜
and
๎˜Œ ๎˜… ๎˜ ๎˜
, we GUESS
๎˜†๎˜ƒ
๎˜Š
๎˜‚ ๎˜ ๎˜‡ ๎˜
Test: using the square formula,
๎˜†๎˜ƒ
๎˜Š
๎˜‚ ๎˜ ๎˜‡ ๎˜ ๎˜…
๎˜‰๎˜Š
๎˜ ๎˜‚ ๎˜‹ ๎˜ƒ
๎˜Š
๎˜‚ ๎˜Œ ๎˜Ž
Ans
๎˜†๎˜ƒ
๎˜Š
๎˜‚ ๎˜ ๎˜‡ ๎˜
Example 2: Factor
๎˜Œ
๎˜Š
๎˜ ๎˜ˆ ๎˜ƒ
๎˜‰๎˜Š ๎˜
๎˜‚ ๎˜‹ ๎˜
๎˜
๎˜
.
Solution
Since
๎˜Œ
๎˜Š
๎˜ ๎˜… ๎˜†๎˜
๎˜Š
๎˜‡๎˜
and
๎˜‹๎˜
๎˜
๎˜ ๎˜… ๎˜†
๎˜‰๎˜
๎˜‡๎˜
, we GUESS
๎˜†๎˜
๎˜Š
๎˜ˆ
๎˜‰ ๎˜
๎˜‡๎˜
Test: using the square formula,
๎˜†๎˜
๎˜Š
๎˜ˆ
๎˜‰ ๎˜
๎˜‡๎˜ ๎˜… ๎˜Œ
๎˜Š
๎˜ ๎˜ˆ ๎˜ƒ
๎˜‰๎˜Š ๎˜
๎˜‚ ๎˜‹ ๎˜
๎˜
๎˜ ๎˜Ž
Ans
๎˜†๎˜
๎˜Š
๎˜ˆ
๎˜‰ ๎˜
๎˜‡๎˜
1
pf3
pf4
pf5

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Download Factoring Formulas: Perfect Square, Difference of Squares, and Difference & Sum of Cubes and more Cheat Sheet Mathematics in PDF only on Docsity!

5.6 Special Factoring Formulas

A. Perfect Square Factoring

  1. Perfect Square Factoring Formulas : ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ and ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 
  2. To use: if the first and last terms of a trinomial are squares, try writing a perfect square; then use the square formula to see if you are correct.
  3. Examples:

Example 1: Factor ^ ^ ^ ^.

Solution

Since ^ ^ ^ ^ ^ ^ and ^ ^ , we GUESS ^ ^ ^ ^ 

Test: using the square formula, ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 

Ans ^ ^ ^ ^ 

Example 2: Factor ^ ^ ^  ^ ^  ^.

Solution

Since ^ ^ ^ ^ ^ and ^  ^ ^ ^  ^ ^ , we GUESS ^ ^  ^ 

Test: using the square formula, ^ ^  ^ ^ ^ ^ ^ ^  ^ ^  ^ 

Ans ^ ^  ^ 

Example 3: Factor ^ ^ ^ ^.

Solution

Since ^ ^ ^ ^ ^ ^ and ^ ^ , we GUESS ^ ^ ^ ^ 

Test: using the square formula, ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ X

This shortcut fails, so we must do AntiFOIL!

    TSP:   

Ans ^ ^ ^ ^ ^ 

B. Difference of Squares

  1. Formula : ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 
  2. Examples:

Example 1: Factor ^ ^.

Solution

Write ^ ^ as ^ ^ 

By the formula, we get

Ans ^ ^ ^ ^ ^ 

C. Difference and Sum of Cubes

  1. Formulas

Difference of Cubes: ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 

Sum of Cubes: ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 

  1. Note : The quadratic in the factorization is prime (no need to try to factor it!)
  2. Easy way to remember these two formulas:

First factor : just โ€œremoveโ€ the cubes

Second factor : pretend to โ€œsquareโ€ the first factor EXCEPT rather than doing product times ^ , do product times 

  1. Examples:

Example 1: Factor ^ ^ ^ ^.

Solution

Write ^ ^ ^ ^ as ^ ^

By the formula, we get

Ans ^ ^ ^ ^ ^ ^ ^ 

Example 2: Factor ^ ^ ^ ^ ^.

Solution

Write ^ ^ ^ ^ ^ as ^ ^ ^ ^ ^ ^ ^ ^

By the formula, we get

Ans ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 

D. Closing Comment

As always when factoring, you should first check to see if you can factor out a GCF before trying any other technique. In the last sections, we will put all of our techniques together.