Rational numbers.pdf
698.4 KB
Main course (M6G)
Lesson 1.3: Rational numbers
In this lesson you will find out about some rational numbers. Comparison of them, laws of addition and multiplication. We'll find out image of a rational number on the coordinate axis. And a few words about equations.
Lesson 1.3: Rational numbers
In this lesson you will find out about some rational numbers. Comparison of them, laws of addition and multiplication. We'll find out image of a rational number on the coordinate axis. And a few words about equations.
Remember, each lesson builds on the previous ones, so I recommend studying them sequentially.Write your questions in the comments, I will be happy to answer 🤓
Task
Difficulty – ⭐️⭐️
Prove that the sum of the squares of three consecutive natural numbers
numbers are not an exact square.
Source: Algebra 10, Pratusevich M. Y.
Difficulty – ⭐️⭐️
Prove that the sum of the squares of three consecutive natural numbers
numbers are not an exact square.
Source: Algebra 10, Pratusevich M. Y.
What the difference between these definitions of rational numbers?
First:
On the other hand, the definition that allows the denominator to be any non-zero integer (m/n, where m is an integer and n is a non-zero integer) has its own advantages. It includes both positive and negative fractions, which can be important in various mathematical contexts, such as algebraic manipulations, number theory, or solving equations involving rational numbers. It preserves the symmetry between positive and negative fractions, providing a more comprehensive view of rational numbers.
Ultimately, the choice of definition depends on the specific requirements and objectives of the mathematical framework or problem being addressed. Both definitions are valid and serve their respective purposes effectively in different mathematical contexts.
First:
m/n is a rational number, where m is an integer and n is a positive number.Second:
m/n is a rational number, where m is an integer and n is non-zero integer.
The definition that restricts the denominator to be a positive number (m/n, where m is an integer and n is a positive number) can be advantageous in certain situations. It ensures that every rational number has a unique representation, simplifies ordering and arithmetic operations, and aligns with the commonly used representation of fractions. It may be particularly useful in elementary mathematics education or contexts where simplicity and ease of computation are prioritized.On the other hand, the definition that allows the denominator to be any non-zero integer (m/n, where m is an integer and n is a non-zero integer) has its own advantages. It includes both positive and negative fractions, which can be important in various mathematical contexts, such as algebraic manipulations, number theory, or solving equations involving rational numbers. It preserves the symmetry between positive and negative fractions, providing a more comprehensive view of rational numbers.
Ultimately, the choice of definition depends on the specific requirements and objectives of the mathematical framework or problem being addressed. Both definitions are valid and serve their respective purposes effectively in different mathematical contexts.
Math From Zero
Task Difficulty – ⭐️⭐️ Prove that the sum of the squares of three consecutive natural numbers numbers are not an exact square. Source: Algebra 10, Pratusevich M. Y.
SolutionThe sum of the squares of three consecutive integers gives a remainder of 2 when divided by 3 (one of these numbers is divisible by 3, the squares of the remaining numbers give a remainder of 1 when divided by 3), which the squares of numbers when divided by 3 cannot give.
👍1
Task
Difficulty – ⭐️⭐️⭐️
A natural number
Source: Algebra 10, Pratusevich M. Y.
Difficulty – ⭐️⭐️⭐️
A natural number
n is such that (n + 1) | 8. Prove that the sum of all natural divisors of n is also divisible by 8.Source: Algebra 10, Pratusevich M. Y.
Theorem of the day
Mean value theorem (
Statement of the theorem:
From a geometric point of view, the theorem states that if the ordinates of both ends of a smooth curve are equal, then there is a point on the curve at which the tangent to the curve is parallel to the abscissa axis.
The mechanical meaning of the theorem is that the body, returning to the starting point, at some point in the course of its motion had zero speed.
The proof of Rolle's Theorem is based on the application of Fermat's theorem, which states that if a function has a local extremum within an interval, then the derivative of the function at that point is equal to zero. Let's look at the proof:
Let the function f(x) be continuous on a closed interval [a, b] and differentiable on an open interval (a, b). Suppose f(a) = f(b). Consider two cases:
Case 1: If f(x) is constant over the entire interval [a, b], then the derivative of f'(x) is zero over the entire interval (a, b). Thus, Rolle's theorem holds because there is a point c inside the interval (a, b) where f'(c) = 0.
Case 2: If f(x) is not constant on the interval [a, b], then it must have extremes (maxima or minima) within this interval. Consider the case of a minimum. Let the point x = c be the minimum point of the function f(x) on the interval [a, b]. Since f(x) is continuous on [a, b] and differentiable on (a, b), Fermat's Theorem guarantees that f'(c) = 0.
Thus, in both cases we get that there is a point c inside the interval (a, b) where f'(c) = 0. This proves Rolle's Theorem.
Mean value theorem (
Rolle's theorem). This theorem is of great importance in the analysis of functions and is related to the behavior of quadratic functions on a given interval.Statement of the theorem:
Let the function f(x) be continuous on a closed interval [a, b] and differentiable on an open interval (a, b). If f(a) = f(b), then there is a point c inside the interval (a, b) such that f'(c) = 0.Rolle's theorem is an important tool for the analysis of quadratic functions and other functions, as it allows you to find extremum points or other singular points on the graph of a function. This theorem also applies to other types of functions, not just quadratic ones.
From a geometric point of view, the theorem states that if the ordinates of both ends of a smooth curve are equal, then there is a point on the curve at which the tangent to the curve is parallel to the abscissa axis.
The mechanical meaning of the theorem is that the body, returning to the starting point, at some point in the course of its motion had zero speed.
The proof of Rolle's Theorem is based on the application of Fermat's theorem, which states that if a function has a local extremum within an interval, then the derivative of the function at that point is equal to zero. Let's look at the proof:
Let the function f(x) be continuous on a closed interval [a, b] and differentiable on an open interval (a, b). Suppose f(a) = f(b). Consider two cases:
Case 1: If f(x) is constant over the entire interval [a, b], then the derivative of f'(x) is zero over the entire interval (a, b). Thus, Rolle's theorem holds because there is a point c inside the interval (a, b) where f'(c) = 0.
Case 2: If f(x) is not constant on the interval [a, b], then it must have extremes (maxima or minima) within this interval. Consider the case of a minimum. Let the point x = c be the minimum point of the function f(x) on the interval [a, b]. Since f(x) is continuous on [a, b] and differentiable on (a, b), Fermat's Theorem guarantees that f'(c) = 0.
Thus, in both cases we get that there is a point c inside the interval (a, b) where f'(c) = 0. This proves Rolle's Theorem.
❤1
History of mathematics
Évariste Galois was born on October 25, 1811 in France. He began to show mathematical talent from an early age and already in his teens he made a number of important discoveries in the field of algebra and number theory. However, his genius was not fully recognized during his lifetime, and he ran into problems in an educational system that was oriented towards more classical and established mathematical methods.
Galois developed the concept of the group, which has become one of the central themes of modern algebra. He also developed field theory, which is of great importance for algebra and mathematics in general. In his work, Galois studied the properties of algebraic extensions and found a way to classify them using groups.
Despite his significant mathematical achievements, Galois's life was short and tragic. At the age of only 20, on May 30, 1832, Galois died in a duel. A conflict between Galois and another mathematician named Charles Hermite led to a challenge to a duel. Some sources state that the duel was due to political differences, while others attribute it to professional jealousy and distrust of Galois's mathematical discoveries.
Galois's death was a great loss to the mathematical community. He passed away early in his career, and many of his ideas and discoveries were realized and appreciated only after his death. Currently, the legacy of Evariste Galois continues to have a huge impact on the development of algebra and mathematics in general.
Évariste Galois was born on October 25, 1811 in France. He began to show mathematical talent from an early age and already in his teens he made a number of important discoveries in the field of algebra and number theory. However, his genius was not fully recognized during his lifetime, and he ran into problems in an educational system that was oriented towards more classical and established mathematical methods.
Galois developed the concept of the group, which has become one of the central themes of modern algebra. He also developed field theory, which is of great importance for algebra and mathematics in general. In his work, Galois studied the properties of algebraic extensions and found a way to classify them using groups.
Despite his significant mathematical achievements, Galois's life was short and tragic. At the age of only 20, on May 30, 1832, Galois died in a duel. A conflict between Galois and another mathematician named Charles Hermite led to a challenge to a duel. Some sources state that the duel was due to political differences, while others attribute it to professional jealousy and distrust of Galois's mathematical discoveries.
Galois's death was a great loss to the mathematical community. He passed away early in his career, and many of his ideas and discoveries were realized and appreciated only after his death. Currently, the legacy of Evariste Galois continues to have a huge impact on the development of algebra and mathematics in general.
Math From Zero
Task Difficulty – ⭐️⭐️⭐️ A natural number n is such that (n + 1) | 8. Prove that the sum of all natural divisors of n is also divisible by 8. Source: Algebra 10, Pratusevich M. Y.
Solution
Note that
Let
If
Note that
n ≡ 7 (mod 8). Let d be a natural divisor of n.Let
n = kd. Iterating over the remainders after dividing by 8, we can see thatIf
d ≡ m (mod 8),That
k ≡ 8 − m (mod 8).Therefore, all divisors of the number
n are divided into pairs, the sum of the numbers in each of which is a multiple of 8.👍1
Exression and set of its values.pdf
493.1 KB
Main course (A7G)
Lesson 1.1: Expression and set of its values
In this lesson you will find out set theory. What is set, how we designate them. Some info about basic statistical characteristics.
Lesson 1.1: Expression and set of its values
In this lesson you will find out set theory. What is set, how we designate them. Some info about basic statistical characteristics.
Remember, each lesson builds on the previous ones, so I recommend studying them sequentially.Write your questions in the comments, I will be happy to answer 🤓
How infinity works: let's explore Hilbert's paradox
Infinity is a concept that has fascinated people for thousands of years. But how does mathematics deal with this mysterious phenomenon? One of the most striking examples of its strange nature is the Hilbert paradox, the story of an infinite hotel that is never full.
What is a Hilbert hotel?
Imagine a hotel with an infinite number of rooms. They are all numbered:
1, 2, 3, 4, ...
One day, an infinite number of guests arrive at this hotel, and each of them occupies a different room. At first glance, the hotel is fully occupied. But what happens if one more guest arrives?
Relocating one guest
The hotel manager finds a way out! He asks each guest from room n to move to room n + 1:
n → n + 1
Now room 1 is free and the new guest can be placed in the vacated space. The infinite hotel can easily handle the new ‘guests’.
What if an infinite number of guests arrive?
Now another infinite group of people are coming to the hotel. How to accommodate them all? The administrator moves all the current guests into rooms with even numbers:
n → 2n
After that, all odd numbers (1, 3, 5, ...) remain vacant and the new guests can occupy them:
k → 2k - 1, where k = 1, 2, 3, ...
Infinity plus infinity: the weirdness does not end
What if an infinite number of infinite groups come to the hotel? Will the hotel be able to cope? The answer is yes!
The receptionist finds a new plan. Let's have:
the current guests move into rooms that are multiples of 2:
n → 2^1 * n,
a new infinite group occupies rooms divisible by 3:
k → 3^1 * k,
the next group occupies rooms divisible by 5, and so on, for all prime numbers.
In this way, each guest can be assigned a unique place using the properties of mutually prime numbers.
What have we learnt about infinity?
The Hilbert Hotel shows that infinity in mathematics does not behave like finite numbers. For example:
∞ + 1 = ∞,
∞ + ∞ = ∞,
even ∞ * ∞ = ∞.
These properties are described using set theory developed by Georg Cantor. For example, the natural numbers and the integers have the same power, even if it seems that there are ‘more’ integers.
Infinity is a concept that has fascinated people for thousands of years. But how does mathematics deal with this mysterious phenomenon? One of the most striking examples of its strange nature is the Hilbert paradox, the story of an infinite hotel that is never full.
What is a Hilbert hotel?
Imagine a hotel with an infinite number of rooms. They are all numbered:
1, 2, 3, 4, ...
One day, an infinite number of guests arrive at this hotel, and each of them occupies a different room. At first glance, the hotel is fully occupied. But what happens if one more guest arrives?
Relocating one guest
The hotel manager finds a way out! He asks each guest from room n to move to room n + 1:
n → n + 1
Now room 1 is free and the new guest can be placed in the vacated space. The infinite hotel can easily handle the new ‘guests’.
What if an infinite number of guests arrive?
Now another infinite group of people are coming to the hotel. How to accommodate them all? The administrator moves all the current guests into rooms with even numbers:
n → 2n
After that, all odd numbers (1, 3, 5, ...) remain vacant and the new guests can occupy them:
k → 2k - 1, where k = 1, 2, 3, ...
Infinity plus infinity: the weirdness does not end
What if an infinite number of infinite groups come to the hotel? Will the hotel be able to cope? The answer is yes!
The receptionist finds a new plan. Let's have:
the current guests move into rooms that are multiples of 2:
n → 2^1 * n,
a new infinite group occupies rooms divisible by 3:
k → 3^1 * k,
the next group occupies rooms divisible by 5, and so on, for all prime numbers.
In this way, each guest can be assigned a unique place using the properties of mutually prime numbers.
What have we learnt about infinity?
The Hilbert Hotel shows that infinity in mathematics does not behave like finite numbers. For example:
∞ + 1 = ∞,
∞ + ∞ = ∞,
even ∞ * ∞ = ∞.
These properties are described using set theory developed by Georg Cantor. For example, the natural numbers and the integers have the same power, even if it seems that there are ‘more’ integers.
Problem of the day
At what angle can a tree 10 metres high be seen from a distance of 800 metres?
1) in radians;
2) in angular minutes.
At what angle can a tree 10 metres high be seen from a distance of 800 metres?
1) in radians;
2) in angular minutes.
Why is 1 not a prime number?
Nobody prevents us from including the number 1 in the definition of a prime number. However, such a definition would be inconvenient in practical applications of the concept of a prime number, including the main such application — the fundamental theorem of arithmetic.
It follows from the fundamental theorem of arithmetic that every natural number greater than 1 has a unique canonical form of notation.
Now it becomes clear why it is inconvenient to consider 1 a prime number. After all, if 1 is a prime number, then the fundamental theorem of arithmetic will not be satisfied. Indeed,
18 = 2 * 3^2 = 1 * 2 * 3^2 = 1^(2009) * 2 * 3^2.
Thus, neither the sets of factors nor the sets of exponents in such a canonical form of notation will coincide.
Nobody prevents us from including the number 1 in the definition of a prime number. However, such a definition would be inconvenient in practical applications of the concept of a prime number, including the main such application — the fundamental theorem of arithmetic.
It follows from the fundamental theorem of arithmetic that every natural number greater than 1 has a unique canonical form of notation.
Now it becomes clear why it is inconvenient to consider 1 a prime number. After all, if 1 is a prime number, then the fundamental theorem of arithmetic will not be satisfied. Indeed,
18 = 2 * 3^2 = 1 * 2 * 3^2 = 1^(2009) * 2 * 3^2.
Thus, neither the sets of factors nor the sets of exponents in such a canonical form of notation will coincide.
👍1
Math From Zero
Why is 1 not a prime number? Nobody prevents us from including the number 1 in the definition of a prime number. However, such a definition would be inconvenient in practical applications of the concept of a prime number, including the main such application…
Fundamental theorem of arithmetic.pdf
82.3 KB
Number theory
Fundamental theorem of arithmetic
Fundamental theorem of arithmetic