Chapter 9: Problem 12
Find the binomial series for the functions. $$\left(1+x^{2}\right)^{3}$$
Short Answer
Expert verified
The binomial series for \((1 + x^2)^3\) is \(1 + 3x^2 + 3x^4 + x^6\).
Step by step solution
01
Define the General Binomial Theorem
The binomial theorem for expanding \((1 + x)^n\) for any integer \(n\), is given by:\[(1 + x)^n = \sum_{k=0}^{n} \binom{n}{k} x^k\]where \(\binom{n}{k}\) is the binomial coefficient, \(\binom{n}{k} = \frac{n!}{k!(n-k)!}\).
02
Substitute into the Binomial Theorem
In this particular problem, we will substitute \(x^2\) for \(x\) and 3 for \(n\). This results in:\[(1 + x^2)^3 = \sum_{k=0}^{3} \binom{3}{k} (x^2)^k\]
03
Calculate Binomial Coefficients
Now calculate the binomial coefficients for \(n=3\):- \(\binom{3}{0} = 1\)- \(\binom{3}{1} = 3\)- \(\binom{3}{2} = 3\)- \(\binom{3}{3} = 1\)Make sure to use these coefficients to expand the expression.
04
Expand the Expression
Substitute the binomial coefficients and powers of \(x^2\) into the series:\[(1 + x^2)^3 = \binom{3}{0}(x^2)^0 + \binom{3}{1}(x^2)^1 + \binom{3}{2}(x^2)^2 + \binom{3}{3}(x^2)^3\]\[= 1(x^0) + 3(x^2) + 3(x^4) + 1(x^6)\]\[= 1 + 3x^2 + 3x^4 + x^6\]
05
Verify the Expansion
To verify, you can re-expand the expression step-by-step or use a calculator to ensure that multiplying out \((1+x^2)(1+x^2)(1+x^2)\) also results in \(1 + 3x^2 + 3x^4 + x^6\).
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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 powerful tool in algebra that allows us to expand expressions of the form \((1 + x)^n\), where \(n\) is any non-negative integer. At its core, the theorem depicts how each term in the expansion is derived.
The expression is represented in a compact form using a summation, as follows:
The expression is represented in a compact form using a summation, as follows:
- \((1 + x)^n = \sum_{k=0}^{n} \binom{n}{k} x^k\)
Binomial Coefficients
Binomial coefficients are a key component of the Binomial Theorem and represent the weights of each term in the polynomial expansion. They are denoted by \(\binom{n}{k}\) and are calculated using factorials:
- \(\binom{n}{k} = \frac{n!}{k!(n-k)!}\)
- \(\binom{3}{0} = 1\)
- \(\binom{3}{1} = 3\)
- \(\binom{3}{2} = 3\)
- \(\binom{3}{3} = 1\)
Polynomial Expansion
Polynomial expansion using the Binomial Theorem effectively breaks down a binomial raised to any power into a series of terms. This is especially helpful in simplifying complex expressions.
In our particular example, \((1 + x^2)^3\) is expanded through replacement of \(x\) with \(x^2\), while maintaining the same binomial structure:
\(1 + 3x^2 + 3x^4 + x^6\).
This method showcases the efficiency of the Binomial Theorem, simplifying what could otherwise be a laborious calculation.
In our particular example, \((1 + x^2)^3\) is expanded through replacement of \(x\) with \(x^2\), while maintaining the same binomial structure:
- First term: \(\binom{3}{0}(x^2)^0 = 1\)
- Second term: \(\binom{3}{1}(x^2)^1 = 3x^2\)
- Third term: \(\binom{3}{2}(x^2)^2 = 3x^4\)
- Fourth term: \(\binom{3}{3}(x^2)^3 = x^6\)
\(1 + 3x^2 + 3x^4 + x^6\).
This method showcases the efficiency of the Binomial Theorem, simplifying what could otherwise be a laborious calculation.