Algebraic Pattern Examples: 47 Problems with Answers

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Algebraic Pattern.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Math.

Concept Recap

A recognizable, recurring algebraic structure such as $a^2 - b^2$ or $(a+b)^2$ that can be applied systematically.

$a^2 - b^2$ always factors to $(a+b)(a-b)$ — recognize the pattern once and apply it everywhere.

Read the full concept explanation →

How to Use These Examples

Read the first worked example with the solution open so the structure is clear.
Try the practice problems before revealing each solution.
Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: An algebraic pattern is a recurring identity like $a^2-b^2$ that you match-and-fill instead of re-deriving.

Common stuck point: The procedure for algebraic pattern is the easy part; the trap is forcing $a^2+b^2$ to factor as $(a+b)(a-b)$ . Asking "Does this expression match the template of a known identity slot-for-slot?" first is what keeps a correct-looking calculation from being attached to the wrong concept.

Sense of Study hint: Ask: Does this expression match the template of a known identity slot-for-slot?

Worked Examples

Example 1

easy

Identify the pattern and factor:

x^2 - 2x + 1

Answer

(x - 1)^2

First step

Step 1: Recognize:

x^2 - 2(x)(1) + 1^2

matches

(a-b)^2 = a^2 - 2ab + b^2

Full solution

2
Step 2: $a = x, b = 1$ , so $(x - 1)^2$ .
3
Check: $(x-1)^2 = x^2 - 2x + 1$ ✓

Pattern recognition speeds up algebra enormously. Recognizing

a^2 \pm 2ab + b^2

as a perfect square trinomial is faster than the sum-product method.

Example 2

hard

Factor

x^3 - 27

by identifying the pattern.

Example 3

medium

Factor

x^2 + 10x + 25

by recognizing a pattern.

Example 4

medium

Recognize the sequence pattern:

1, 3, 6, 10, 15, \dots

. Closed form for

a_n

Example 5

hard

Recognize and factor:

x^4 + 4x^2 + 4 - 9x^2

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy

What pattern does

9x^2 - 16

match?

Example 2

medium

Simplify

\frac{x^3 + 8}{x + 2}

Example 3

easy

Factor

x^2 - 9

by recognizing the pattern.

Example 4

easy

Expand

(x+5)^2

using the perfect-square pattern.

Example 5

easy

x^2 + 4

a difference of squares?

Example 6

easy

What pattern fits

x^2 - 6x + 9

, and what does it factor to?

Example 7

easy

Identify the next term in the pattern

2, 4, 8, 16, \dots

and give a formula for the

n

-th term.

Example 8

easy

Factor

x^2 + 7x + 12

by finding the additive/multiplicative pattern.

Example 9

easy

Recognize the pattern:

1, 4, 9, 16, \dots

. What is the

n

-th term?

Example 10

easy

Factor the sum of cubes

x^3 + 8

using the pattern.

Example 11

medium

Factor

4x^2 - 25

by recognizing the disguised pattern.

Example 12

medium

The sequence

2, 5, 10, 17, 26, \dots

follows what pattern? Give a formula for

a_n

Example 13

medium

Use a pattern to compute

99 \times 101

without long multiplication.

Example 14

medium

Factor

x^4 - 16

completely by applying patterns repeatedly.

Example 15

medium

A trinomial

x^2 + bx + 9

is a perfect square. Find all values of

b

Example 16

medium

Recognize the pattern and factor

x^2 - 5x - 14

Example 17

medium

The pattern

\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}

telescopes. Recognize the term pattern and sum it.

Example 18

medium

Generalize: the pattern

1+3+5+\dots+(2n-1)

equals what closed form? Verify for

n=4

Example 19

medium

Factor

x^3 - 27

by recognizing the difference-of-cubes pattern.

Example 20

challenge

Find a closed form for

a_n

given

a_1=1

and

a_n = a_{n-1}+2n-1

, by recognizing the accumulated pattern.

Example 21

challenge

For which integer

n

n^4 + 4

factorable over the integers as a product of two quadratics? Use the Sophie Germain pattern.

Example 22

challenge

Recognize the pattern in

\binom{n}{0}+\binom{n}{1}+\dots+\binom{n}{n}

and prove the closed form using the binomial theorem.

Example 23

easy

Factor

x^2 - 49

using a pattern.

Example 24

easy

Expand

(x - 4)^2

using the perfect-square pattern.

Example 25

easy

Factor

x^3 - 64

Example 26

easy

Expand

(2x + 3)^2

Example 27

easy

Recognize the next term:

3, 6, 12, 24, \dots

and give a closed form.

Example 28

medium

Use a pattern to compute

103^2 - 97^2

Example 29

medium

Factor

9x^2 + 30x + 25

Example 30

medium

Factor completely:

x^4 - 81

Example 31

medium

Simplify

\dfrac{x^3 - 27}{x - 3}

for

x \ne 3

Example 32

medium

Find

b

so that

x^2 + bx + 36

is a perfect square.

Example 33

medium

Factor

x^3 + 125

using the sum-of-cubes pattern.

Example 34

hard

Factor

x^6 - 64

completely.

Example 35

hard

Use a pattern to compute

1^2 + 2^2 + 3^2 + \dots + 10^2

Example 36

hard

Simplify

\dfrac{a^2 - b^2}{a - b}

for

a \ne b

Example 37

hard

Use a pattern to find

\sum_{k=1}^{n} k^3

for

n = 5

Example 38

hard

Compute

(101)(99)

using a pattern.

Example 39

medium

Factor

50 - 2x^2

completely.

Example 40

medium

Identify and apply: factor

x^2 + 2xy + y^2 - 9

Example 41

challenge

Compute

S = 1 - 2 + 3 - 4 + \dots + 99 - 100

by recognizing a pattern.

Example 42

challenge

Find a closed form for the telescoping sum

\sum_{k=1}^{n} \dfrac{1}{k(k+1)}

← Back to Algebraic Pattern Formula Explained Practice Mode

Related Concepts

Expressions Factoring Algebraic Identities

Background Knowledge

These ideas may be useful before you work through the harder examples.

expressions