Problem 84 - College Algebra

Question

Perform the indicated operation or operations. $$ (5 x+2 y)^{2}-(5 x-2 y)^{2} $$

Step-by-Step Solution

Answer

Therefore, the simplified form of the expression \( (5x+2y)^{2} - (5x - 2y)^{2}\) is \(40xy\).

Step 1: Expand the Binomials

Using the binomial formulas, the first term is expanded as \((5x + 2y)^{2} = (5x)^{2} + 2(5x)(2y) + (2y)^{2} = 25x^{2} + 20xy + 4y^{2}\) and the second term is expanded as \((5x - 2y)^{2} = (5x)^{2} - 2(5x)(2y) + (2y)^{2} = 25x^{2} - 20xy + 4y^{2}\)

Step 2: Subtract the Second Result from the First

Subtracting the result of the second equation from the first results in \((25x^{2} + 20xy + 4y^{2}) - (25x^{2} - 20xy + 4y^{2}) = 25x^{2} + 20xy + 4y^{2} - 25x^{2} + 20xy - 4y^{2}\)

Step 3: Combine Like Terms

Here, we add up the like terms: \(25x^{2} - 25x^{2} + 20xy + 20xy + 4y^{2} - 4y^{2} = 40xy\). So, the solution is 40xy

Key Concepts

Binomial Expansion Simplified

The binomial theorem allows us to expand expressions that are raised to any power in a very structured way. A binomial is an algebraic expression that has two terms, such as \((5x + 2y)\). When we raise a binomial to a power, we use a specific formula to expand it.

This expansion involves taking each term in the binomial, raising it to powers in decreasing order, and multiplying them by binomial coefficients. For example, in \((5x + 2y)^2\), the expansion becomes:

• The first term squared: \((5x)^2 = 25x^2\)
• Two times the product of both terms: \(2(5x)(2y) = 20xy\)
• The second term squared: \((2y)^2 = 4y^2\)

All these are added together to produce \(25x^2 + 20xy + 4y^2\). Understanding binomial expansion requires familiarity with multiplying binomials and using binomial coefficients, which can be derived from Pascal's triangle or using combinations formula.

Recognizing and Combining Like Terms

Like terms in algebra are those that have the same variables raised to the same powers, even if their coefficients are different. When simplifying expressions, it is essential to combine these like terms.

In our exercise, after expanding the binomials, we are left with terms such as \(25x^2\) and \(-25x^2\), as well as \(20xy\) and \(-20xy\), among others. Terms like \(25x^2\) and \(-25x^2\) cancel each other out because they are like terms, simplifying our expression further.

The reason for combining like terms is to simplify the expression to its simplest form, making it easier to solve or further manipulate. Here, after combining, you find the solution as \(40xy\), showing how powerful understanding this concept is in algebra.

Understanding Polynomials

A polynomial is an algebraic expression that consists of multiple terms, each made up of a coefficient, a variable, and an exponent. Polynomials can be simple, like \(x^2 + 2x + 1\), or more complex with multiple variables and powers, like our expression.

Polynomials are classified based on their degree, which is the highest power of the variable in the expression. For example, the degree of \(x^2 + 2x + 1\) is 2.

Understanding polynomials is crucial because they appear in various areas of mathematics, including calculus and quadratic functions. They are used to model various real-world systems. In our given task, applying operations to polynomials correctly, such as addition or subtraction, helped us simplify the given expression.