Chapter 3: Problem 81
Write a polynomial \(f(x)\) that meets the given conditions. Answers may vary. (See Example 10 ) Degree 2 polynomial with zeros of \(7+8 i\) and \(7-8 i\).
Short Answer
Expert verified
The polynomial is \( f(x) = x^2 - 14x + 113 \).
Step by step solution
01
Understand the Problem
It is given that the polynomial should be of degree 2 and have zeros at 7+8i and 7-8i. For a degree 2 polynomial, the general form is: \(f(x) = a(x-r_1)(x-r_2)\), where \(r_1\) and \(r_2\) are the zeros.
02
Write the Polynomial Using Given Zeros
Substitute the given zeros \(7+8i\) and \(7-8i\) into the polynomial form: \(f(x) = a(x-(7+8i))(x-(7-8i))\).
03
Simplify the Expression
Simplify the expression. First subtract the complex numbers inside the parentheses: \(f(x) = a((x-7-8i)(x-7+8i))\).
04
Apply Difference of Squares
Use the difference of squares formula, \((x-a)(x+b) = x^2-(b^2)\), to simplify further: \(f(x) = a((x-7)^2-(8i)^2)\).
05
Simplify Complex Numbers
Simplify the complex number term \( (8i)^2 = -64 \): \(f(x) = a((x-7)^2-(-64))\).
06
Combine and Expand
Combine terms and expand \((x-7)^2 - (-64) = (x-7)^2 + 64\). Expand \((x-7)^2 = x^2 - 14x + 49\): \( f(x) = a (x^2 - 14x + 49 + 64 )\). Simplify further: \( f(x) = a (x^2 - 14x + 113)\).
07
Determine the Leading Coefficient
Choose the leading coefficient, \(a\), to be 1 for simplicity: \( f(x) = x^2 - 14x + 113\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Zeros of Polynomial
Zerоs of a polynоmiаl refer to thе values оf x for which the polynоmiаl evaluatеs to zero. Essentially, these are the solutions or roots of the polynomial equation. For instance, if the polynomial is given by \(f(x) = x^2 - 14x + 113\), the zeros are found by solving the equation \(f(x) = 0\). In this case, the given values are complex numbers, \(7+8i\) and \(7-8i\). Here’s how this works:
- Each zero represents a solution for \(x\) in the polynomial equation \(f(x) = 0\).
- A polynomial of degree \(n\) has exactly \(n\) zeros, which may include real and complex numbers.
Degree of Polynomial
The degree of a polynomial refers to the highest power of the variable \(x\) in the polynomial expression. It is a crucial concept since it determines the number of zeros a polynomial can have and the general behavior of the polynomial at very large or very small values of \(x\). For example, in the polynomial \(f(x) = x^2 - 14x + 113\), the highest power of \(x\) is \(2\), making this a degree \(2\) polynomial. Here’s why it matters:
- A degree 2 polynomial, also called a quadratic polynomial, will have up to 2 zeros.
- The shape and characteristics of the polynomial graph are heavily influenced by its degree.
Complex Numbers
Complex numbers are numbers that include an imaginary component along with a real component and are usually written in the form \(a + bi\) where \(i\) is the imaginary unit satisfying \(i^2 = -1\). The given exercise involved zeros that were complex numbers: \(7+8i\) and \(7-8i\). Here’s an overview of the complex numbers:
- Real Part: The real component, denoted as \(a\) in \(a+bi\), is a standard real number.
- Imaginary Part: The imaginary component, denoted as \(bi\), includes the imaginary unit \(i\) which squared equals \(-1\).
- Conjugates: Complex conjugates are pairs like \(7+8i\) and \(7-8i\). They have the same real part but opposite imaginary parts.