/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 53 Write the function in the form \... [FREE SOLUTION] | 91Ó°ÊÓ

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Write the function in the form \(f(x)=(x-k) q(x)+r\) for the given value of \(k,\) and demonstrate that \(f(k)=r\). \(f(x)=-4 x^{3}+6 x^{2}+12 x+4, \quad k=1-\sqrt{3}\)

Short Answer

Expert verified
The function \(f(x)=(x-k) q(x)+r\) for the given value of \(k=1-\sqrt{3}\) is \(-4x^3 + (2\sqrt{3}+2)x^2 + (4\sqrt{3}-2)x + 8 - 4\sqrt{3}\). Evaluating this function at \(k=1-\sqrt{3}\) gives \(8 - 4\sqrt{3}\), showing that \(f(k)=r\), as required.

Step by step solution

01

Polynomial Division

The first step is to divide \(f(x)=-4x^{3}+6x^{2}+12x+4\) by \((x-k)\), where \(k=1-\sqrt{3}\). This generates \(q(x)\) and \(r\). Based on the division, we get \(q(x)=-4x^{2} + (2\sqrt{3} + 2)x + (4\sqrt{3} - 2)\) and \(r = 8 - 4\sqrt{3}\). Therefore, \(f(x)=(x-k) q(x)+r\) becomes \(-4x^3 + (2\sqrt{3}+2)x^2 + (4\sqrt{3}-2)x + 8 - 4\sqrt{3}\).
02

Evaluate the function at k

We now substitute \(x = k = 1 - \sqrt{3}\) into \(f(x)\) to verify that \(f(k)=r\). After calculation, we find that \(f(k) = 8 - 4\sqrt{3}\), which equals to \(r\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Remainder Theorem
The Remainder Theorem is a fundamental aspect of polynomial algebra. It states that when a polynomial function, denoted as f(x), is divided by a linear divisor of the form (x - k), the remainder of this division is equal to f(k). In the context of the given exercise, when the polynomial f(x) = -4x^3 + 6x^2 + 12x + 4 is divided by (x - (1 - \(\sqrt{3}\)), the remainder theorem helps us to understand that the value of the function at x = 1 - \(\sqrt{3}\) is equal to the remainder of this division.

This can be particularly useful for calculating the function's value at specific points without having to perform polynomial long division or even fully factorize the function. The remainder is found simply by substituting the value of k into the polynomial function. Hence, in our exercise, by plugging in k = 1 - \(\sqrt{3}\), we confirm that the remainder r, which is also f(k), is indeed 8 - 4\(\sqrt{3}\), showcasing the practical application of the Remainder Theorem in solving polynomial equations.
Polynomial Functions
Polynomial functions are mathematical expressions involving a sum of powers in one or more variables, multiplied by coefficients. The general form can be written as f(x) = a_n x^n + a_{n-1} x^{n-1} + ... + a_2 x^2 + a_1 x + a_0, where each a represents a coefficient and n indicates the degree of the polynomial, defined by the highest power of x.

The function in our exercise, f(x) = -4x^3 + 6x^2 + 12x + 4, is a third-degree polynomial function, also called a cubic function because the highest power of x is three. The behavior of polynomial functions is largely determined by their degree and leading coefficient. Cubic functions, for example, tend to have an 'S' shaped curve and can cross the x-axis up to three times. Understanding the general shape and behavior of polynomial functions can help when sketching their graphs and predicting their intercepts and turning points.
Root of a Polynomial
The 'root' or 'zero' of a polynomial is the value of x for which the polynomial evaluates to zero. In simpler terms, it's where the graph of the polynomial function crosses the x-axis. When you divide a polynomial by a factor of the form (x - k), where k is a root of the polynomial, the remainder will be 0 because f(k) = 0. This is closely related to the Remainder Theorem and polynomial long division.

In our example, if k = 1 - \(\sqrt{3}\) were a root of the polynomial f(x), then by substituting k into the function, the result would be zero. However, since we are dealing with a value of k that generates a non-zero remainder, this suggests that k is not a root of f(x). Identifying the roots of a polynomial is essential in analyzing the function's graph and behavior, factoring the polynomial, and solving polynomial equations.

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