Chapter 11: Problem 341
For the following exercises, use the Binomial Theorem to expand each binomial. $$\left(\frac{1}{x}+3 y\right)^{5}$$
Short Answer
Expert verified
The expanded form is \( \frac{1}{x^5} + \frac{15y}{x^4} + \frac{90y^2}{x^3} + \frac{270y^3}{x^2} + \frac{405y^4}{x} + 243y^5 \).
Step by step solution
01
Understand the Binomial Theorem
The Binomial Theorem provides a way to expand expressions of the form \((a + b)^n\). It states that \((a+b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k\). In this expression, \( \binom{n}{k} \) is a binomial coefficient calculated as \( \frac{n!}{k!(n-k)!} \).
02
Identify Parameters
In the expression \( \left( \frac{1}{x} + 3y\right)^5 \), identify \( a = \frac{1}{x} \), \( b = 3y \), and \( n = 5 \). These will be substituted into the binomial expansion formula.
03
Calculate Each Term Using the Binomial Theorem
Calculate each term using the formula \( T_k = \binom{n}{k} a^{n-k} b^k \) for \( k = 0 \) to \( n = 5 \):- For \( k = 0 \), \( T_0 = \binom{5}{0} \left(\frac{1}{x}\right)^5 (3y)^0 = 1 \cdot \frac{1}{x^5} \cdot 1 = \frac{1}{x^5} \).- For \( k = 1 \), \( T_1 = \binom{5}{1} \left(\frac{1}{x}\right)^4 (3y)^1 = 5 \cdot \frac{1}{x^4} \cdot 3y = \frac{15y}{x^4} \).- For \( k = 2 \), \( T_2 = \binom{5}{2} \left(\frac{1}{x}\right)^3 (3y)^2 = 10 \cdot \frac{1}{x^3} \cdot 9y^2 = \frac{90y^2}{x^3} \).- For \( k = 3 \), \( T_3 = \binom{5}{3} \left(\frac{1}{x}\right)^2 (3y)^3 = 10 \cdot \frac{1}{x^2} \cdot 27y^3 = \frac{270y^3}{x^2} \).- For \( k = 4 \), \( T_4 = \binom{5}{4} \left(\frac{1}{x}\right)^1 (3y)^4 = 5 \cdot \frac{1}{x} \cdot 81y^4 = \frac{405y^4}{x} \).- For \( k = 5 \), \( T_5 = \binom{5}{5} \left(\frac{1}{x}\right)^0 (3y)^5 = 1 \cdot 1 \cdot 243y^5 = 243y^5 \).
04
Write the Expanded Form
Combine the terms from Step 3 to write the expanded form of the binomial:\[ \left( \frac{1}{x} + 3y \right)^5 = \frac{1}{x^5} + \frac{15y}{x^4} + \frac{90y^2}{x^3} + \frac{270y^3}{x^2} + \frac{405y^4}{x} + 243y^5 \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Expansion
Expanding a binomial expression using the Binomial Theorem is a powerful tool in algebra. The Binomial Theorem formula \[ (a+b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k \]gives us a way to express any binomial raised to a power as a sum of terms. Each term in the expansion is constructed using specific components:
- The base expressions, \( a \) and \( b \), are the two terms inside the binomial.
- The exponent \( n \), which is the power to which the binomial is raised.
- And finally, the terms \( T_k = \binom{n}{k} a^{n-k} b^k \) involve binomial coefficients and powers of \( a \) and \( b \).
Binomial Coefficient
Binomial coefficients play a crucial role in expanding expressions using the Binomial Theorem. They are denoted as \( \binom{n}{k} \) and can be calculated using the formula:\[ \binom{n}{k} = \frac{n!}{k!(n-k)!} \]Here, \( n! \) denotes the factorial of \( n \), which is the product of all positive integers up to \( n \). The binomial coefficient \( \binom{n}{k} \) gives the number of ways to choose \( k \) elements from a set of \( n \) elements without regard to order.
- For each term in the binomial expansion, a specific binomial coefficient is used to calculate the correct term.
- The term \( \binom{n}{k} \) represents how the exponents of \( a \) and \( b \) are distributed through the expansion process.
- This coefficient ensures that each term is correctly balanced within the polynomial.
Polynomial Expression
A polynomial expression is a mathematical expression made up of variables and constants combined using addition, subtraction, multiplication, and non-negative integer exponents. These expressions can vary from a simple combination of terms to more complex formulas.
- After applying the Binomial Theorem, the expanded form of a binomial becomes a polynomial expression.
- The expression takes the form of multiple terms added together, each consisting of constant coefficients, variables, and powers.
- In the expansion process, each term's degree is based on the sum of the exponents of its variables, such as \( x \) and \( y \), in our example.