Chapter 11: Problem 30
Use the binomial formula to expand each binomial. $$(3+2 a)^{4}$$
Short Answer
Expert verified
The expanded form is \(81 + 216a + 216a^2 + 96a^3 + 16a^4\).
Step by step solution
01
Identify the Binomial Formula
The binomial formula for expansion is given by the expression: \[(x+y)^n = \sum_{k=0}^{n} \binom{n}{k} x^{n-k} y^k\] where \(n\) is the exponent, \(\binom{n}{k}\) is the binomial coefficient, \(x\) is the first term in the binomial, and \(y\) is the second term.
02
Set the Values
For the expression \((3+2a)^4\), set \(x = 3\), \(y = 2a\), and \(n = 4\). We will use these values to expand the binomial using the formula.
03
Calculate the Binomial Coefficients
Calculate the binomial coefficients \(\binom{4}{k}\) for \(k = 0\) to \(4\):- \(\binom{4}{0} = 1\)- \(\binom{4}{1} = 4\)- \(\binom{4}{2} = 6\)- \(\binom{4}{3} = 4\)- \(\binom{4}{4} = 1\)
04
Apply the Binomial Formula
Substitute the coefficients and terms into the binomial formula: - For \(k=0\): \(\binom{4}{0} (3)^{4} (2a)^{0} = 1 \cdot 81 \cdot 1 = 81\)- For \(k=1\): \(\binom{4}{1} (3)^{3} (2a)^{1} = 4 \cdot 27 \cdot 2a = 216a\)- For \(k=2\): \(\binom{4}{2} (3)^{2} (2a)^{2} = 6 \cdot 9 \cdot 4a^2 = 216a^2\)- For \(k=3\): \(\binom{4}{3} (3)^{1} (2a)^{3} = 4 \cdot 3 \cdot 8a^3 = 96a^3\)- For \(k=4\): \(\binom{4}{4} (3)^{0} (2a)^{4} = 1 \cdot 1 \cdot 16a^4 = 16a^4\)
05
Write the Expanded Form
Combine all the terms together to write the expanded form of the binomial: \[(3 + 2a)^4 = 81 + 216a + 216a^2 + 96a^3 + 16a^4\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Theorem
The binomial theorem is a crucial mathematical tool that allows us to expand expressions that are raised to a power, specifically binomials. A binomial is an expression containing two terms. The formula for the binomial theorem is expressed as:
- The general form: \[(x+y)^n = \sum_{k=0}^{n} \binom{n}{k} x^{n-k} y^k\]
- The summation symbol \(\sum\) indicates that you add up all the terms from \(k = 0\) to \(k = n\).
- The binomial coefficient \(\binom{n}{k}\) is calculated using combinations, which can be found using factorial notation.
Algebraic Expressions
An algebraic expression is a mathematical phrase that can contain numbers, variables (like \(a\), \(b\)) and operators (such as +, -, *, /). Algebraic expressions are the building blocks of algebra, helping us model real-world situations and solve various equations.
When dealing with binomials, the expression often includes:
When dealing with binomials, the expression often includes:
- Constants: Numbers with fixed values, such as the '3' in our given binomial \((3+2a)^4\).
- Variables: Symbols that represent numbers or values, like 'a' in the expression.
- Coefficients: Numbers that multiply the variables, indicated by '2' in '2a'.
Polynomial Expansion
Polynomial expansion involves expressing a binomial raised to a power as a sum of terms, each consisting of a coefficient, variable parts, and constants. The expanded polynomial is often easier to use in further calculations and provides insight into the nature of the expression.
In the example \((3+2a)^4\), polynomial expansion through the binomial theorem leads us to:
In the example \((3+2a)^4\), polynomial expansion through the binomial theorem leads us to:
- Multiple terms: It results in five terms: \(81, 216a, 216a^2, 96a^3, \text{and }16a^4\).
- Simplified computation: By expanding, we can easily compute specific values or solve equations involving the polynomial.
- Insight into terms: The expansion shows the contribution of each individual part of the binomial to the final polynomial.