Chapter 5: Problem 40
For the following exercises, find the zeros and give the multiplicity of each. $$ f(x)=2 x^{4}\left(x^{3}-4 x^{2}+4 x\right) $$
Short Answer
Expert verified
Zeros: 0 (multiplicity 5), 2 (multiplicity 2).
Step by step solution
01
Rewrite the Polynomial
Begin by rewriting the function as \[ f(x) = 2x^4 (x^3 - 4x^2 + 4x) \]Observe that there's a common factor inside the parentheses. Factor the expression inside the parentheses further.
02
Factor Completely
Factor the cubic polynomial inside the parentheses:\[ x^3 - 4x^2 + 4x = x(x^2 - 4x + 4) \]The quadratic \( x^2 - 4x + 4 \) can be factored into \((x-2)^2\), resulting in:\[ x(x-2)^2 \]So the function is now \[ f(x) = 2x^4 \times x \times (x-2)^2\] which simplifies to \[ f(x) = 2x^5(x-2)^2 \].
03
Find the Zeros
Set the function equal to zero and solve for \(x\): \[ 2x^5(x-2)^2 = 0 \].This equation gives us two factors to solve: 1. \( 2x^5 = 0 \)2. \( (x-2)^2 = 0 \).
04
Solve for Zeros
Solve each factor separately:1. \( 2x^5 = 0 \) implies \( x = 0 \).2. \( (x-2)^2 = 0 \) implies \( x = 2 \).Thus, the zeros are \( x = 0 \) and \( x = 2 \).
05
Determine Multiplicity
The multiplicity of a zero is determined by the exponent of its corresponding factor:- For \( x = 0 \), the factor is \( x^5 \) so the multiplicity is 5.- For \( x = 2 \), the factor is \( (x-2)^2 \) so the multiplicity is 2.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Zero Multiplicity
In mathematics, the zero of a polynomial is the value of \( x \) that makes the entire polynomial equal to zero. Each zero can also have something known as a multiplicity, which tells us how many times that particular zero is repeated in the polynomial. Consider the polynomial from the exercise, which is \( f(x) = 2x^5(x-2)^2 \). When we factorize the expression, the terms \( x^5 \) and \( (x-2)^2 \) reveal the zeros of the polynomial.
- For the zero at \( x = 0 \), the factor \( x^5 \) indicates that this zero occurs 5 times because the exponent is 5. Therefore, the multiplicity of \( x = 0 \) is 5.
- For the zero at \( x = 2 \), the factor \( (x-2)^2 \) indicates that this zero occurs 2 times because the exponent here is 2. Thus, the multiplicity of \( x = 2 \) is 2.
Factoring Polynomials
Factoring polynomials is a fundamental process in algebra that involves breaking down a polynomial into simpler polynomials that can be multiplied together to obtain the original polynomial. In simpler terms, it's about finding the building blocks of a polynomial. In the exercise, the polynomial \( f(x) = 2x^4(x^3 - 4x^2 + 4x) \) is factored to make it easier to find its zeros.
Let's take a closer look at the factoring process:
Let's take a closer look at the factoring process:
- Firstly, you observe the polynomial \( x^3 - 4x^2 + 4x \) inside the parentheses and note common factors. Here, \( x \) is a common factor, which can be factored out, resulting in \( x(x^2 - 4x + 4) \).
- Secondly, the quadratic \( x^2 - 4x + 4 \) can be further factored into \((x-2)^2\).
Cubic Polynomials
Cubic polynomials are those of degree three, which means they include terms up to \( x^3 \). They often take the form \( ax^3 + bx^2 + cx + d \). In our exercise, the function includes a cubic polynomial, \( x^3 - 4x^2 + 4x \), which we needed to simplify further.When dealing with cubic polynomials:
- Identify any common factor in all terms. Here, the common factor was \( x \), leading to \( x(x^2 - 4x + 4) \).
- Look out for patterns or formulas that make further factoring feasible, such as grouping terms or identifying perfect squares.
Quadratic Factoring
Quadratic factoring involves breaking down a polynomial expression of degree two into a product of simpler expressions. Quadratics generally have the form \( ax^2 + bx + c \). In the provided solution, we encountered a quadratic within the cubic polynomial: \( x^2 - 4x + 4 \).Here's how quadratic factoring works:
- Look for patterns, such as perfect square trinomials, which can be rewritten as squares of binomials, like \((x-2)^2\) in this case.
- Apply known formulas or techniques, such as factoring by grouping or using the quadratic formula when needed.