Chapter 30: Problem 20
Find the first three nonzero terms of the Maclaurin expansion of the given functions. $$f(x)=(2 x-1)^{2}$$
Short Answer
Expert verified
The first three nonzero terms are \( 1 - 4x + 4x^2 \).
Step by step solution
01
Identify the function and Maclaurin Series
The Maclaurin series is a specific case of the Taylor series expansion around 0. We need the first three nonzero terms of the series for the function \( f(x) = (2x-1)^2 \).
02
Express the function in terms of Maclaurin series
First, note that according to the binomial expansion, \( (2x - 1)^2 = 1 - 4x + 4x^2 \). Since this is a quadratic polynomial, it can also be considered as its own Maclaurin series.
03
Verify the first few terms
We expand \( (2x - 1)^2 = 1 - 4x + 4x^2 \) into the form of a power series about x=0 and identify the terms as such: the constant term is 1, the coefficient of the linear term \( x \) is \(-4\), and the coefficient of the quadratic term \( x^2 \) is \(4\).
04
Concatenate the nonzero terms
Since there are no higher-order terms needed for this function (due to its quadratic nature), the first three nonzero terms of the Maclaurin expansion are directly from the expression: \( 1 - 4x + 4x^2 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Binomial Expansion
The binomial expansion is a powerful tool in mathematics that allows us to expand expressions involving two terms raised to a power, such as \((a + b)^n\).This concept simplifies calculations and is widely applied in various mathematical problems, including calculus and algebra.For \((2x - 1)^2\), applying the binomial expansion simplifies the expression by following the formula: \((a - b)^2 = a^2 - 2ab + b^2\).
- Identify the terms: here, \(a = 2x\) and \(b = 1\).
- Calculate the expanded form: \((2x)^2 - 2(2x)(1) + 1^2\).
- After simplification, we get: \((2x - 1)^2 = 4x^2 - 4x + 1\).
Exploring Power Series
A power series is an infinite series of the form \(a_0 + a_1x + a_2x^2 + a_3x^3 + \ldots\).It allows representation of functions in a way that expresses them as sums of powers of \(x\).
In our specific function \(f(x) = (2x - 1)^2\), the first three terms of its power series expansion about \(x=0\) provide the approximation as \(1 - 4x + 4x^2\).This shows:
In our specific function \(f(x) = (2x - 1)^2\), the first three terms of its power series expansion about \(x=0\) provide the approximation as \(1 - 4x + 4x^2\).This shows:
- The constant term, \(a_0 = 1\).
- The linear term, \(a_1 = -4\).
- The quadratic term, \(a_2 = 4\).
Quadratic Polynomials Demystified
Quadratic polynomials are algebraic expressions of the form \(ax^2 + bx + c\), where \(a, b,\) and \(c\) are constants, and \(a ≠0\).This is essentially a polynomial of degree 2.For example, in the expression \((2x - 1)^2\), the function simplifies to \(4x^2 - 4x + 1\).
- Here, \(a = 4\),
- \(b = -4\),
- and \(c = 1\).
- They graph as a parabola.
- They have at most two roots.
- The vertex form reveals maximum or minimum points.
The Magic of Taylor Series
The Taylor series is a way to represent a function as an infinite sum of terms calculated from the values of its derivatives at a single point. When the expansion is taken around \(x = 0\), it's called the Maclaurin series.
The general Taylor series formula around a point \(a\) is:\[ f(x) = f(a) + f'(a)(x-a) + \frac{f''(a)}{2!}(x-a)^2 + \ldots \]For our function \(f(x) = (2x-1)^2\), finding the Maclaurin series, which is simply the Taylor series about 0, gives us: \(1 - 4x + 4x^2\).
The general Taylor series formula around a point \(a\) is:\[ f(x) = f(a) + f'(a)(x-a) + \frac{f''(a)}{2!}(x-a)^2 + \ldots \]For our function \(f(x) = (2x-1)^2\), finding the Maclaurin series, which is simply the Taylor series about 0, gives us: \(1 - 4x + 4x^2\).
- The constant term corresponds to \(f(a)\).
- The linear term to \(f'(a)\).
- The quadratic term to \(\frac{f''(a)}{2!}\).