Identifying a Sum of Cubes

Oct 13, 2025 by wbrum.org 114 views

Introduction

In algebra, a sum of cubes is a polynomial expression that can be factored into the product of three binomials. It is a fundamental concept in mathematics, and understanding how to identify and factor a sum of cubes is crucial for solving various mathematical problems. In this article, we will explore the concept of a sum of cubes and determine which polynomial expression among the given options represents a sum of cubes.

What is a Sum of Cubes?

A sum of cubes is a polynomial expression of the form $a^3 + b^3$ , where $a$ and $b$ are algebraic expressions. It can be factored into the product of three binomials using the formula:

a^3 + b^3 = (a + b)(a^2 - ab + b^2)

This formula allows us to factor a sum of cubes into a product of three binomials, making it easier to solve mathematical problems.

Identifying a Sum of Cubes

To identify a sum of cubes, we need to look for a polynomial expression that can be written in the form $a^3 + b^3$ . We can do this by examining the terms of the polynomial expression and looking for pairs of terms that are cubes.

For example, consider the polynomial expression $x^3 + 8x^3$ . We can see that both terms are cubes, and therefore, this expression represents a sum of cubes.

Analyzing the Options

Now that we have a good understanding of what a sum of cubes is and how to identify one, let's analyze the options given in the problem.

Option A: $(6-s)\left(s^2+6s+36\right)$

To determine if this expression represents a sum of cubes, we need to examine the terms of the expression. We can see that the first term is $(6-s)$ , and the second term is $\left(s^2+6s+36\right)$ . However, we cannot see if this expression is a sum of cubes by just looking at the terms.

Option B: $(6+s)\left(s^2-6s-36\right)$

Similarly, we need to examine the terms of this expression to determine if it represents a sum of cubes. We can see that the first term is $(6+s)$ , and the second term is $\left(s^2-6s-36\right)$ . However, we cannot see if this expression is a sum of cubes by just looking at the terms.

Option C: $(6+s)\left(s^2-6s+36\right)$

Let's examine the terms of this expression. We can see that the first term is $(6+s)$ , and the second term is $\left(s^2-6s+36\right)$ . We can rewrite the second term as $\left(s^2-6s+36\right) = (s-6)^2 + 36$ . However, we cannot see if this expression is a sum of cubes by just looking at the terms.

Option D: $(6+s)\left(s^2+6s+36\right)$

Let's examine the terms of this expression. We can see that the first term is $(6+s)$ , and the second term is $\left(s^2+6s+36\right)$ . We can rewrite the second term as $\left(s^2+6s+36\right) = (s+6)^2 + 36$ . This expression can be rewritten as $(s+6)^3 - 6^3$ , which is a sum of cubes.

Conclusion

In conclusion, the polynomial expression that represents a sum of cubes is option D: $(6+s)\left(s^2+6s+36\right)$ . This expression can be rewritten as $(s+6)^3 - 6^3$ , which is a sum of cubes.

Final Answer

Introduction

In our previous article, we explored the concept of a sum of cubes and determined which polynomial expression among the given options represents a sum of cubes. In this article, we will answer some frequently asked questions (FAQs) about sum of cubes.

Q: What is a sum of cubes?

A: A sum of cubes is a polynomial expression of the form $a^3 + b^3$ , where $a$ and $b$ are algebraic expressions. It can be factored into the product of three binomials using the formula:

a^3 + b^3 = (a + b)(a^2 - ab + b^2)

Q: How do I identify a sum of cubes?

A: To identify a sum of cubes, you need to look for a polynomial expression that can be written in the form $a^3 + b^3$ . You can do this by examining the terms of the polynomial expression and looking for pairs of terms that are cubes.

Q: What is the formula for factoring a sum of cubes?

A: The formula for factoring a sum of cubes is:

a^3 + b^3 = (a + b)(a^2 - ab + b^2)

Q: Can I factor a sum of cubes into a product of three binomials?

A: Yes, you can factor a sum of cubes into a product of three binomials using the formula:

a^3 + b^3 = (a + b)(a^2 - ab + b^2)

Q: What is the difference between a sum of cubes and a difference of cubes?

A: A sum of cubes is a polynomial expression of the form $a^3 + b^3$ , while a difference of cubes is a polynomial expression of the form $a^3 - b^3$ . The formula for factoring a difference of cubes is:

a^3 - b^3 = (a - b)(a^2 + ab + b^2)

Q: Can I use the formula for factoring a sum of cubes to factor a difference of cubes?

A: No, you cannot use the formula for factoring a sum of cubes to factor a difference of cubes. The formula for factoring a difference of cubes is:

a^3 - b^3 = (a - b)(a^2 + ab + b^2)

Q: What are some examples of sum of cubes?

A: Some examples of sum of cubes include:

$x^3 + 8x^3$
$(2x)^3 + (3x)^3$
$x^3 + 27$

Q: Can I use the formula for factoring a sum of cubes to factor a polynomial expression that is not a sum of cubes?

A: No, you cannot use the formula for factoring a sum of cubes to factor a polynomial expression that is not a sum of cubes. The formula is only applicable to polynomial expressions that can be written in the form $a^3 + b^3$ .

Conclusion

In conclusion, we have answered some frequently asked questions (FAQs) about sum of cubes. We hope that this article has provided you with a better understanding of the concept of a sum of cubes and how to identify and factor one.

Final Answer

The final answer is that a sum of cubes is a polynomial expression of the form $a^3 + b^3$ , which can be factored into the product of three binomials using the formula:

a^3 + b^3 = (a + b)(a^2 - ab + b^2)