Chapter 1: Problem 12
Express as a polynomial. $$(x+3 y)^{3}$$
Short Answer
Expert verified
The polynomial is \(x^3 + 9x^2 y + 27xy^2 + 27y^3\).
Step by step solution
01
Apply the Binomial Theorem
The Binomial Theorem states that \((a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k\). In this case, \(a = x\), \(b = 3y\), and \(n = 3\). We will expand \((x + 3y)^3\) using this formula.
02
Calculate Each Term Independently
Substitute into the Binomial Theorem: \[(x + 3y)^3 = \sum_{k=0}^{3} \binom{3}{k} x^{3-k} (3y)^k\]This gives us individual terms: - For \(k = 0\): \(\binom{3}{0} x^3 (3y)^0 = x^3\) - For \(k = 1\): \(\binom{3}{1} x^2 (3y)^1 = 3x^2 \cdot 3y = 9x^2 y\) - For \(k = 2\): \(\binom{3}{2} x^1 (3y)^2 = 3x \cdot 9y^2 = 27x y^2\) - For \(k = 3\): \(\binom{3}{3} x^0 (3y)^3 = 27y^3\)
03
Sum All Calculated Terms
Now, add all the terms from Step 2 to express the polynomial:\[x^3 + 9x^2 y + 27xy^2 + 27y^3\].This polynomial is the final expanded form of \((x + 3y)^3\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Expansion
Polynomial expansion is a fundamental concept in algebra. It involves transforming an expression with exponents into a series of terms. In our example, we expand \((x+3y)^{3}\) into a polynomial. This means we will rewrite it as a sum of multiple terms without exponents. Polynomial expansion is especially useful for simplifying expressions and solving equations.
- The process uses rules and formulas, such as the Binomial Theorem, to break down complex expressions into simpler parts.
- This transformation helps us to better understand the structure and function of algebraic expressions.
Binomial Coefficients
Binomial coefficients play a key role in expanding expressions like \((x+3y)^3\). These coefficients are the numbers that multiply the terms in the polynomial. They arise from the Binomial Theorem, represented by \(\binom{n}{k}\), where \(n\) is the total exponent and \(k\) is the specific term index.
- The binomial coefficient tells us how many ways we can choose \(k\) items from \(n\) items, which directly influences the terms' multiplication factor during expansion.
- For example, the coefficients for \((x+3y)^{3}\) are found from \(\binom{3}{k}\) for \(k = 0, 1, 2, 3\).
- This results in coefficients 1, 3, 3, and 1, which are used to scale the corresponding terms \(x^{3-k} (3y)^k\).
Algebraic Expressions
Algebraic expressions are combinations of numbers, variables, and operations. They form the backbone of algebra and include terms like \(x, 3y,\) and \(x^3\). In our exercise, \((x+3y)^3\) is expanded into another algebraic expression: \(x^3 + 9x^2 y + 27xy^2 + 27y^3\).
- Each term in the expression represents a distinct component that contributes to the expression's value.
- By manipulating variables and coefficients, algebraic expressions can be added, subtracted, multiplied, and divided.
- When expanding \((x+3y)^3\), each term, like \(9x^2y\), results from combining coefficients with powers of \(x\) and \(y\).