Chapter 10: Problem 38
Use the Binomial Theorem to expand the given expression. $$ \left(3-y^{2}\right)^{4} $$
Short Answer
Expert verified
The expanded form is \(81 - 108y^2 + 54y^4 - 12y^6 + y^8\).
Step by step solution
01
Identify the Components
The expression \((3 - y^2)^4\) can be expanded using the Binomial Theorem. Here, \(a = 3\), \(b = -y^2\), and \(n = 4\). The Binomial Theorem states that \((a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k\).
02
Calculate Binomial Coefficients
The binomial coefficients for \(n = 4\) are given by \(\binom{4}{k}\) for \(k = 0\) to \(4\). These coefficients are: - \(\binom{4}{0} = 1\) - \(\binom{4}{1} = 4\) - \(\binom{4}{2} = 6\) - \(\binom{4}{3} = 4\) - \(\binom{4}{4} = 1\).
03
Apply the Binomial Theorem
Using the coefficients and the Binomial Theorem, we expand \((3 - y^2)^4\) as:\[(3 - y^2)^4 = \sum_{k=0}^{4} \binom{4}{k} (3)^{4-k} (-y^2)^k\].
04
Compute Each Term
Calculate each term of the expansion:- For \(k = 0\): \(\binom{4}{0}(3)^4(-y^2)^0 = 1 \times 81 \times 1 = 81\).- For \(k = 1\): \(\binom{4}{1}(3)^3(-y^2)^1 = 4 \times 27 \times (-y^2) = -108y^2\).- For \(k = 2\): \(\binom{4}{2}(3)^2(-y^2)^2 = 6 \times 9 \times y^4 = 54y^4\).- For \(k = 3\): \(\binom{4}{3}(3)^1(-y^2)^3 = 4 \times 3 \times (-y^6) = -12y^6\).- For \(k = 4\): \(\binom{4}{4}(3)^0(-y^2)^4 = 1 \times 1 \times y^8 = y^8\).
05
Write the Final Expansion
Combine all the calculated terms to write the final expanded expression:\((3 - y^2)^4 = 81 - 108y^2 + 54y^4 - 12y^6 + y^8\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Coefficients
When working with the Binomial Theorem, a key aspect is understanding binomial coefficients. These coefficients are critical for determining the weights or multipliers of each term in a binomial expansion. Binomial coefficients are represented as \( \binom{n}{k} \), which is read as "n choose k." This expression gives the number of ways to choose \(k\) elements from a set of \(n\) elements, and is calculated using the formula:\[\binom{n}{k} = \frac{n!}{k!(n-k)!}\]where \(!\) denotes factorial, meaning the product of all positive integers up to that number. For instance, for \(n = 4\) and \(k = 2\), the binomial coefficient is:\[\binom{4}{2} = \frac{4!}{2!(4-2)!} = \frac{24}{4} = 6\]These coefficients straightforwardly guide us in building each term of the polynomial that results from a binomial expansion.
Algebraic Expressions
An algebraic expression is a combination of numbers, variables, and operators such as addition or subtraction. In the context of the Binomial Theorem, expressions take the specific form of a binomial, which is an algebraic expression containing exactly two terms. For example, \((3 - y^2)\) is a binomial because it contains two distinct parts: a constant \(3\) and a term involving the variable \(-y^2\).It's essential to correctly identify and manipulate the two terms separately to apply the Binomial Theorem effectively:- Numeric terms (constants)- Variable termsAlgebraic expressions can be expanded, combined, or simplified using various algebraic rules, including the Binomial Theorem, which systematically deals with expressions raised to a power.
Polynomial Expansion
Polynomial expansion is the process of expressing a binomial raised to a power as a polynomial, a multi-term expression. The Binomial Theorem provides a systematic way to achieve this expansion through step-by-step multiplication of the binomial, using the structure of binomial coefficients and powers.The Binomial Theorem formula: \[(a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k\]allows us to expand expressions like \((3 - y^2)^4\).In expanding:- Each term in the polynomial is formed by choosing a different power \(k\) for \(b\), resulting in alternating positive and negative signs based on \(b^k\).- The coefficients \(\binom{n}{k}\) provide the correct multiplier for each term.Thus, you can observe how starting with the simple binomial leads to a complex polynomial encompassing various powers and terms, like transforming \((3 - y^2)^4\) into a detailed polynomial \(81 - 108y^2 + 54y^4 - 12y^6 + y^8\). This process uncovers the relationships between terms and their coefficients, enhancing understanding of algebra and its applications.