Chapter 3: Problem 10
Use the remainder theorem to find \(f(c)\). $$f(x)=2 x^{3}+4 x^{2}-3 x-1 ; \quad c=3$$
Short Answer
Expert verified
The value of \(f(3)\) is 80.
Step by step solution
01
State the Remainder Theorem
The Remainder Theorem states that the remainder of the division of a polynomial \(f(x)\) by \(x-c\) is \(f(c)\). Thus, finding \(f(c)\) will give us the remainder of the polynomial when divided by \(x-c\).
02
Calculate \(f(3)\)
Substitute \(c = 3\) into the polynomial \(f(x) = 2x^3 + 4x^2 - 3x - 1\). So, calculate: \[f(3) = 2(3)^3 + 4(3)^2 - 3(3) - 1\]
03
Simplification of \(f(3)\)
First, calculate \((3)^3 = 27\) and \((3)^2 = 9\). Substitute these values back into the equation: \[f(3) = 2 \times 27 + 4 \times 9 - 3 \times 3 - 1\]
04
Complete the Calculation
Calculate each term: - \(2 \times 27 = 54\), - \(4 \times 9 = 36\), - \(3 \times 3 = 9\). Now, plug these into the equation to get: \[f(3) = 54 + 36 - 9 - 1\]
05
Find the Result of \(f(3)\)
Add and subtract the numbers: \[f(3) = 54 + 36 - 9 - 1 = 80\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Division
Polynomial division is a method used to divide polynomials, similar to the way we perform division with numbers. However, dividing polynomials involves more steps and understanding. The main goal is to express a polynomial as the product of a divisor and a quotient, plus a remainder, which mirrors the structure: \[ \frac{\text{Dividend} - \text{Remainder}}{\text{Divisor}} = \text{Quotient} \]. When dividing a polynomial, the remainder has a smaller degree than the divisor. This is a crucial point, as it is what makes the Remainder Theorem applicable.
- Polynomial division can be done using long division or synthetic division techniques.
- The degree of the remainder is always less than the degree of the divisor.
- The division process helps to simplify polynomials in equations and calculus.
Evaluating Polynomials
Evaluating polynomials involves finding the value of the polynomial function at a particular point, such as at a specific value of x. This process is incredibly important, not only in finding solutions to equations but also in applying mathematical models to real-world situations. For example, if we have a polynomial function \(f(x)\), and we need to find \(f(c)\), we substitute \(x\) with \(c\) in the polynomial. The idea is to compute:
- First replace every instance of \(x\) with \(c\).
- Carry out arithmetic operations in the polynomial after substitution.
Polynomial Remainder
The polynomial remainder is what remains after performing polynomial division. According to the Remainder Theorem, the remainder obtained when a polynomial \(f(x)\) is divided by a linear divisor \(x-c\) is simply \(f(c)\). This direct computation of the remainder without actual division saves time and effort.When considering the Remainder Theorem:
- The theorem only applies when dividing by a linear factor such as \(x-c\).
- The process involves evaluating the polynomial at \(c\) to find the remainder.
- This remainder helps determine how closely a point \((c, f(c))\) fits the polynomial function.
Polynomial Functions
Polynomial functions are crucial building blocks in mathematics, represented by algebraic expressions involving a sum of powers of variables. Each term in a polynomial function is composed of a coefficient and a variable raised to a non-negative integer power. Polynomials can be classified by degree, with the highest power determining it. For instance, a polynomial like \(f(x) = 2x^3 + 4x^2 - 3x - 1\) is a cubic polynomial with four terms. Here’s why polynomial functions are important:
- They appear in a wide range of scientific calculations and mathematical problems.
- Understanding them leads to insights in calculus, algebra, and even physics.
- They model real-life situations, like physics equations or economic models.