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Roots of polynomial equations

Source: licencja: CC 0.

Pierwiastki równań wielomianowych

Learning objectives

You will develop the ability to factorize polynomials.

You will get to know the method of solving polynomial equations presented in the factored form.

Learning effect

  • You will learn to factorize polynomials.

  • You will learn to solve polynomial equations presented in the factored form.

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nagranie abstraktu

Recollect the most important information about equations and techniques of solving them. In particular, recollect the equivalent equations method and the ancients’ method of analysis (analisis antiquorum).

The aim of the class will be solving polynomial equations.

Using all available sources and the information about equations and methods of solving them, that you have already acquired, define the polynomial equation.

polynomial equation
Definition: polynomial equation
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nagranie abstraktu

The polynomial equationpolynomial equationpolynomial equation of degree n is an equation that can be transformed equivalently to the form Wx=0, where W(x) is a polynomial of degree n(nN+).

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nagranie abstraktu

Analyse the applet, paying special attention to the number of roots of the polynomial equation. Formulate a conclusion.

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Aplet geogebry: Wykresy funkcji wielomianowych. Poniżej znajduje się galeria ilustracji stanowiących alternatywę dla apletu.
Source: GroMar, licencja: CC BY 3.0.
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nagranie abstraktu

The conclusion
In the set of real numbers the polynomial of degree n(nN+) can have no more than n roots.

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nagranie abstraktu

In the available sources you will find the information that the property you have just discovered is called the fundamental theorem of algebra.

Using the information, solve the tasks.

Task 1
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nagranie abstraktu

Find the number of roots of the equationnumber of roots of the equationnumber of roots of the equation.

  1. 3x2-2-xx2-4x+52=0

  2. 2x2x2+4x-72x3-8=0

  3. x2+62x-52x-3=0

Task 2
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nagranie abstraktu

Check which of the numbers -3,-1,1 is the root of the polynomial Wx=x3-x2+3x-3.

Task 3
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nagranie abstraktu

Find number a, when you know that number 2 is the root of the polynomial Wx=x5+x3+ax2-8.

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nagranie abstraktu

Think about what is the simplest method of solving the polynomial equationpolynomial equationpolynomial equation of degree larger than 2?

You will easily notice that the simplest method (in case of polynomials that have roots) is factorizing them to the degree no greater than 2. The students work individually to solve the task using this method.

Task 4
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nagranie abstraktu

Give all the roots of the polynomial Wx=3x-1x2-94x+2.

Task 5
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nagranie abstraktu

Factorize the polynomial Wx=125x4-125x3-8x+8.

Then, solve the equationequationequation Wx=0

Task 6
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nagranie abstraktu

Solve the equationequationequation.

  1. x4+2x3-x-2=0

  2. 8x4+24x3+x+3=0

Task 7
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nagranie abstraktu

Extra task

The product of a given square number and a square number which is larger than this number by 4 equals 2025. Find these numbers. (Answer: the numbers are (-9) and (-5) and also (5 and 9).

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nagranie abstraktu

Having finished all the tasks, do the consolidation tasks.

Remember:
The polynomial equationpolynomial equationpolynomial equation of degree n is an equation that can be transformed equivalently to the form Wx=0, where W(x) is a polynomial of degree n(nN+) can have no more than n roots.

Exercises

Exercise 1
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Wersja alternatywna ćwiczenia: One of the roots of polynomial W(x)=(x4-4)(x+5) is number: Możliwe odpowiedzi: 1. 2, 2. 5, 3. -52, 4. 1
Rzadanie
Source: GroMar, licencja: CC BY 3.0.
Exercise 2

Cream is packaged in a cuboid‑shaped cardboard box whose volume is 0,4 l. The altitude of the box is 6 cm shorter than the edge of the base. The base of the box is a square. Find the dimensions of the box.

Exercise 3

Describe the solution to this equation in English.

x2+4x3-22x-72=0

Exercise 4
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Wersja alternatywna ćwiczenia: Indicate which pairs of expressions or words are translated correctly. Możliwe odpowiedzi: 1. równanie - equation, 2. równanie wielomianowe - polynomial equation, 3. pierwiastki równania - roots of the equation, 4. liczba pierwiastków równania - number of roots of the equation, 5. rozkład wielomianu - short multiplication formulas, 6. wykresy funkcji wielomianowych - roots of the equation
zadanie
Source: GroMar, licencja: CC BY 3.0.
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Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.
Source: Zespół autorski Politechniki Łódzkiej, licencja: CC BY 3.0.

Glossary

equation
equation

równanie

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wymowa w języku angielskim: equation
factorization
factorization

rozkład wielomianu

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wymowa w języku angielskim: factorization
fundamental theorem of algebra
fundamental theorem of algebra

zasadnicze twierdzenie algebry

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wymowa w języku angielskim: fundamental theorem of algebra
graphs of polynomial functions
graphs of polynomial functions

wykresy funkcji wielomianowych

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wymowa w języku angielskim: graphs of polynomial functions
number of roots of the equation
number of roots of the equation

liczba pierwiastków równania

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wymowa w języku angielskim: number of roots of the equation
polynomial equation
polynomial equation

równanie wielomianowe

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wymowa w języku angielskim: polynomial equation
roots of the equation
roots of the equation

pierwiastki równania

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wymowa w języku angielskim: roots of the equation
short multiplication formulas
short multiplication formulas

wzory skróconego mnożenia

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wymowa w języku angielskim: short multiplication formulas

Keywords

equationequationequation

polynomial equationpolynomial equationpolynomial equation – the equation form

roots of the equationroots of the equationroots of the equation

number of roots of the equationnumber of roots of the equationnumber of roots of the equation

factorizationfactorizationfactorization