Breaking Down the Expressions

Oct 13, 2025 by wbrum.org 96 views

**One of these expressions reduces to 1 and the other reduces to -1. Do you know which one is which? How do you know?**

Understanding the Problem

When dealing with mathematical expressions, it's essential to understand the properties and behaviors of different operations. In this case, we're given two expressions:

$\frac{x+3}{3+x}$
$\frac{3-x}{x-3}$

Our goal is to determine which expression reduces to 1 and which one reduces to -1.

Breaking Down the Expressions

To tackle this problem, let's start by analyzing each expression separately.

Expression 1: $\frac{x+3}{3+x}$

This expression can be simplified by recognizing that the numerator and denominator are in the form of a difference of squares. However, we can also approach this by using the concept of conjugate pairs.

A conjugate pair is a pair of expressions that have the same terms but with opposite signs. In this case, the conjugate pair of $x+3$ is $3+x$ . By multiplying both the numerator and denominator by the conjugate pair, we can eliminate the complex fraction.

\frac{x+3}{3+x} \cdot \frac{3-x}{3-x} = \frac{(x+3)(3-x)}{(3+x)(3-x)}

Simplifying the numerator and denominator, we get:

\frac{(x+3)(3-x)}{(3+x)(3-x)} = \frac{3x - x^2 - 9 + 3x}{9 - x^2}

Further simplifying, we get:

\frac{3x - x^2 - 9 + 3x}{9 - x^2} = \frac{6x - x^2 - 9}{9 - x^2}

Now, let's focus on the numerator. We can factor out a $-1$ from the first two terms:

\frac{6x - x^2 - 9}{9 - x^2} = \frac{-(x^2 - 6x + 9)}{9 - x^2}

Recognizing that $x^2 - 6x + 9$ is a perfect square trinomial, we can rewrite it as:

\frac{-(x^2 - 6x + 9)}{9 - x^2} = \frac{-(x-3)^2}{9 - x^2}

Now, let's simplify the denominator by recognizing that it's a difference of squares:

\frac{-(x-3)^2}{9 - x^2} = \frac{-(x-3)^2}{(3-x)(3+x)}

We can now see that the expression is equal to:

\frac{-(x-3)^2}{(3-x)(3+x)} = -1

Expression 2: $\frac{3-x}{x-3}$

This expression can be simplified by recognizing that it's a reciprocal of the expression we analyzed earlier.

\frac{3-x}{x-3} = \frac{-(x-3)}{3-x}

We can now see that this expression is equal to:

\frac{-(x-3)}{3-x} = 1

Conclusion

In conclusion, we've determined that:

Expression 1: $\frac{x+3}{3+x}$ reduces to -1
Expression 2: $\frac{3-x}{x-3}$ reduces to 1

Q&A

Q: How do I know which expression reduces to 1 and which one reduces to -1?

A: To determine which expression reduces to 1 and which one reduces to -1, we need to analyze each expression separately. By simplifying the expressions and recognizing the properties of different operations, we can determine which expression is equal to 1 and which one is equal to -1.

Q: What is the key concept that I need to understand to solve this problem?

A: The key concept that you need to understand to solve this problem is the concept of conjugate pairs and the properties of different operations. By recognizing the conjugate pair of $x+3$ as $3+x$ , we can simplify the expression and determine which one reduces to 1 and which one reduces to -1.

Q: Can I use any other method to solve this problem?

A: Yes, you can use any other method to solve this problem. However, the method we used in this article is a straightforward and efficient way to determine which expression reduces to 1 and which one reduces to -1.

Q: What are some common mistakes that I should avoid when solving this problem?

A: Some common mistakes that you should avoid when solving this problem include:

Not recognizing the conjugate pair of $x+3$ as $3+x$
Not simplifying the expressions correctly
Not recognizing the properties of different operations

By avoiding these common mistakes, you can ensure that you solve the problem correctly and efficiently.