Product of positive quotient dividend and divisor. Terms and concepts of quotient of integers

Only because for integers you need to calculate the sign of the quotient. How to calculate the sign of the quotient of integers? Let's look at it in detail in the topic.

Terms and concepts of quotient of integers.

To perform division of integers, you need to remember terms and concepts. In division there is: the dividend, the divisor and the quotient of integers.

Dividend is the integer that is being divided. Divider is the integer that is being divided by. Private is the result of dividing integers.

You can say “Division of integers” or “Quotient of integers”; the meaning of these phrases is the same, that is, you need to divide one integer by another and get the answer.

Division originates from multiplication. Let's look at an example:

We have two factors 3 and 4. But let’s say we know that there is one factor 3 and the result of multiplying the factors is their product 12. How to find the second factor? Division comes to the rescue.

Rule for dividing integers.

Definition:

Quotient of two integers is equal to the quotient of their modules, with a plus sign as a result if the numbers have the same signs, and with a minus sign if they have different signs.

It is important to consider the sign of the quotient of integers. Brief rules for dividing integers:

Plus on plus gives plus.
“+ : + = +”

Two negatives make an affirmative.
“– : – =+”

Minus plus plus gives minus.
“– : + = –”

Plus times minus gives minus.
“+ : – = –”

Now let's look in detail at each point of the rule for dividing integers.

Dividing positive integers.

Recall that positive integers are the same as natural numbers. We use the same rules as for division natural numbers. The quotient sign for dividing integers positive numbers always a plus. In other words, when dividing two integers “ plus on plus gives plus”.

Example:
Divide 306 by 3.

Solution:
Both numbers have a “+” sign, so the answer will be a “+” sign.
306:3=102
Answer: 102.

Example:
Divide the dividend 220286 by the divisor 589.

Solution:
The dividend of 220286 and the divisor of 589 have a plus sign, so the quotient will also have a plus sign.
220286:589=374
Answer: 374

Dividing negative integers.

The rule for dividing two negative numbers.

Let us have two negative integers a and b. We need to find their modules and perform division.

The result of division or the quotient of two negative integers will have a “+” sign. or "two negatives make an affirmative".

Let's look at an example:
Find the quotient -900:(-12).

Solution:
-900:(-12)=|-900|:|-12|=900:12=75
Answer: -900:(-12)=75

Example:
Divide one negative integer -504 by the second a negative number -14.

Solution:
-504:(-14)=|-504|:|-14|=504:14=34
The expression can be written more briefly:
-504:(-14)=34

Dividing integers with different signs. Rules and examples.

By doing dividing integers with different signs , the quotient will be equal to a negative number.

Whether a positive integer is divided by a negative integer or a negative integer is divided by a positive integer, the result of division will always be equal to a negative number.

Minus plus plus gives minus.
Plus times minus gives minus.

Example:
Find the quotient of two integers with different signs -2436:42.

Solution:
-2436:42=-58

Example:
Calculate division 4716:(-524).

Solution:
4716:(-524)=-9

Zero divided by an integer. Rule.

When zero is divided by an integer, the answer is zero.

Example:
Perform division 0:558.

Solution:
0:558=0

Example:
Divide zero by the negative integer -4009.

Solution:
0:(-4009)=0

You cannot divide by zero.

You cannot divide 0 by 0.

Checking partial division of integers.

As stated earlier, division and multiplication are closely related. Therefore, to check the result of dividing two integers, you need to multiply the divisor and the quotient, resulting in the dividend.

Checking the division result is a short formula:
Divisor ∙ Quotient = Dividend

Let's look at an example:
Perform division and check 1888:(-32).

Solution:
Pay attention to the signs of integers. The number 1888 is positive and has a “+” sign. The number (-32) is negative and has a “–” sign. Therefore, when dividing two integers with different signs, the answer will be a negative number.
1888:(-32)=-59

Now let’s check the found answer:
1888 – divisible,
-32 – divisor,
-59 – private,

We multiply the divisor by the quotient.
-32∙(-59)=1888

The function a n =f (n) of the natural argument n (n=1; 2; 3; 4;...) is called a number sequence.

Numbers a 1; a 2 ; a 3 ; a 4 ;…, forming a sequence, are called members of a numerical sequence. So a 1 =f (1); a 2 =f (2); a 3 =f (3); a 4 =f (4);…

So, the members of the sequence are designated by letters indicating indices - serial numbers their members: a 1 ; a 2 ; a 3 ; a 4 ;…, therefore, a 1 is the first member of the sequence;

a 2 is the second term of the sequence;

a 3 is the third member of the sequence;

a 4 is the fourth term of the sequence, etc.

Briefly the numerical sequence is written as follows: a n =f (n) or (a n).

There are the following ways to specify a number sequence:

1) Verbal method. Represents a pattern or rule for the arrangement of members of a sequence, described in words.

Example 1. Write a sequence of all non-negative numbers, multiples of 5.

Solution. Since all numbers ending in 0 or 5 are divisible by 5, the sequence will be written like this:

0; 5; 10; 15; 20; 25; ...

Example 2. Given the sequence: 1; 4; 9; 16; 25; 36; ... . Ask it verbally.

Solution. We notice that 1=1 2 ; 4=2 2 ; 9=3 2 ; 16=4 2 ; 25=5 2 ; 36=6 2 ; ... We conclude: given a sequence consisting of squares of natural numbers.

2) Analytical method. The sequence is given by the formula of the nth term: a n =f (n). Using this formula, you can find any member of the sequence.

Example 3. The expression for the kth term of a number sequence is known: a k = 3+2·(k+1). Compute the first four terms of this sequence.

a 1 =3+2∙(1+1)=3+4=7;

a 2 =3+2∙(2+1)=3+6=9;

a 3 =3+2∙(3+1)=3+8=11;

a 4 =3+2∙(4+1)=3+10=13.

Example 4. Determine the rule for composing a numerical sequence using its first few members and express the general term of the sequence using a simpler formula: 1; 3; 5; 7; 9; ... .

Solution. We notice that we are given a sequence of odd numbers. Any odd number can be written in the form: 2k-1, where k is a natural number, i.e. k=1; 2; 3; 4; ... . Answer: a k =2k-1.

3) Recurrent method. The sequence is also given by a formula, but not by a general term formula, which depends only on the number of the term. A formula is specified by which each next term is found through the previous terms. In the case of the recurrent method of specifying a function, one or several first members of the sequence are always additionally specified.

Example 5. Write out the first four terms of the sequence (a n ),

if a 1 =7; a n+1 = 5+a n .

a 2 =5+a 1 =5+7=12;

a 3 =5+a 2 =5+12=17;

a 4 =5+a 3 =5+17=22. Answer: 7; 12; 17; 22; ... .

Example 6. Write out the first five terms of the sequence (b n),

if b 1 = -2, b 2 = 3; b n+2 = 2b n +b n+1 .

b 3 = 2∙b 1 + b 2 = 2∙(-2) + 3 = -4+3=-1;

b 4 = 2∙b 2 + b 3 = 2∙3 +(-1) = 6 -1 = 5;

b 5 = 2∙b 3 + b 4 = 2∙(-1) + 5 = -2 +5 = 3. Answer: -2; 3; -1; 5; 3; ... .

4) Graphic method. The numerical sequence is given by a graph, which represents isolated points. The abscissas of these points are natural numbers: n=1; 2; 3; 4; ... . Ordinates are the values ​​of the sequence members: a 1 ; a 2 ; a 3 ; a 4 ;… .

Example 7. Write down all five terms of the numerical sequence given graphically.

Every point in this coordinate plane has coordinates (n; a n). Let's write down the coordinates of the marked points in ascending order of the abscissa n.

We get: (1 ; -3), (2 ; 1), (3 ; 4), (4 ; 6), (5 ; 7).

Therefore, a 1 = -3; a 2 =1; a 3 =4; a 4 =6; a 5 =7.

Answer: -3; 1; 4; 6; 7.

Reviewed number sequence as a function (in example 7) is given on the set of the first five natural numbers (n=1; 2; 3; 4; 5), therefore, is finite number sequence(consists of five members).

If a number sequence as a function is given on the entire set of natural numbers, then such a sequence will be an infinite number sequence.

The number sequence is called increasing, if its members are increasing (a n+1 >a n) and decreasing, if its members are decreasing(a n+1

An increasing or decreasing number sequence is called monotonous.

Very large and very small numbers are usually written in standard form: a∙10 n, Where 1≤a<10 And n(natural or integer) – is the order of a number written in standard form.

For example, 345.7=3.457∙10 2; 123456=1.23456∙10 5 ; 0.000345=3.45∙10 -4.

Examples.

Write the number in standard form: 1) 40503; 2) 0,0023; 3) 876,1; 4) 0,0000067.

Solution.

1) 40503=4.0503·10 4;

2) 0,0023=2,3∙10 -3 ;

3) 876,1=8,761∙10 2 ;

4) 0,0000067=6,7∙10 -6 .

More examples on the standard form of numbers.

5) The number of gas molecules in 1 cm 3 at 0°C and a pressure of 760 mm ps.st is equal to

27 000 000 000 000 000 000.

Solution.

27 000 000 000 000 000 000=2,7∙10 19 .

6) 1 parsec(unit of length in astronomy) is equal to 30,800,000,000,000 km. Write this number in standard form.

Solution.

1 parsec=30 800 000 000 000=3.08∙10 13 km.

To the point:

Kilowatt hour is an off-system unit of energy or work, used in electrical engineering, denoted kWh.

1 kWh=3.6∙10 6 J(Joules).

Often you need to find the sum of squares (x 1 2 +x 2 2) or the sum of cubes (x 1 3 +x 2 3) of the roots of a quadratic equation, less often - the sum of the reciprocal values ​​of the squares of the roots or the sum of arithmetic square roots of the roots of a quadratic equation:

Vieta's theorem can help with this:

Sum of roots of the reduced quadratic equation x 2 +px+q=0 is equal to the second coefficient taken with the opposite sign, and the product of the roots is equal to the free term:

x 1 + x 2 = -p; x 1 ∙x 2 =q.

Let's express through p And q:

1) sum of squares of the roots of the equation x 2 +px+q=0;

2) sum of cubes of the roots of the equation x 2 +px+q=0.

Solution.

1) Expression x 1 2 +x 2 2 obtained by squaring both sides of the equation x 1 + x 2 = -p;

(x 1 +x 2) 2 =(-p) 2 ; open the brackets: x 1 2 +2x 1 x 2 + x 2 2 =p 2 ; we express the required amount: x 1 2 +x 2 2 =p 2 -2x 1 x 2 =p 2 -2q. We got a useful equality: x 1 2 +x 2 2 =p 2 -2q.

2) Expression x 1 3 +x 2 3 Let us represent the sum of cubes using the formula:

(x 1 3 +x 2 3)=(x 1 +x 2)(x 1 2 -x 1 x 2 +x 2 2)=-p·(p 2 -2q-q)=-p·(p 2 -3q).

Another useful equation: x 1 3 +x 2 3 = -p·(p 2 -3q).

Examples.

3) x 2 -3x-4=0. Without solving the equation, calculate the value of the expression x 1 2 +x 2 2.

Solution.

x 1 +x 2 =-p=3, and the work x 1 ∙x 2 =q=in example 1) equality:

x 1 2 +x 2 2 =p 2 -2q. We have -p=x 1 +x 2 = 3 → p 2 =3 2 =9; q= x 1 x 2 = -4. Then x 1 2 +x 2 2 =9-2·(-4)=9+8=17.

Answer: x 1 2 +x 2 2 =17.

4) x 2 -2x-4=0. Calculate: x 1 3 +x 2 3 .

Solution.

By Vieta's theorem, the sum of the roots of this reduced quadratic equation is x 1 +x 2 =-p=2, and the work x 1 ∙x 2 =q=-4. Let's apply what we have received ( in example 2) equality: x 1 3 +x 2 3 =-p·(p 2 -3q)= 2·(2 2 -3·(-4))=2·(4+12)=2·16=32.

Answer: x 1 3 +x 2 3 =32.

Question: what if we are given an unreduced quadratic equation? Answer: it can always be “reduced” by dividing term by term by the first coefficient.

5) 2x 2 -5x-7=0. Without deciding, calculate: x 1 2 +x 2 2.

Solution. We are given a complete quadratic equation. Divide both sides of the equality by 2 (the first coefficient) and obtain the following quadratic equation: x 2 -2.5x-3.5=0.

According to Vieta's theorem, the sum of the roots is equal to 2,5 ; the product of the roots is equal -3,5 .

We solve it in the same way as the example 3) using the equality: x 1 2 +x 2 2 =p 2 -2q.

x 1 2 +x 2 2 =p 2 -2q= 2,5 2 -2∙(-3,5)=6,25+7=13,25.

Answer: x 1 2 + x 2 2 = 13,25.

6) x 2 -5x-2=0. Find:

Let us transform this equality and, using Vieta’s theorem, replace the sum of roots through -p, and the product of the roots through q, we get another useful formula. When deriving the formula, we used equality 1): x 1 2 +x 2 2 =p 2 -2q.

In our example x 1 +x 2 =-p=5; x 1 ∙x 2 =q=-2. We substitute these values ​​into the resulting formula:

7) x 2 -13x+36=0. Find:

Let's transform this sum and get a formula that can be used to find the sum of arithmetic square roots from the roots of a quadratic equation.

We have x 1 +x 2 =-p=13; x 1 ∙x 2 =q=36. We substitute these values ​​into the resulting formula:

Advice : always check the possibility of finding the roots of a quadratic equation using a suitable method, because 4 reviewed useful formulas allow you to quickly complete a task, especially in cases where the discriminant is an “inconvenient” number. In all simple cases, find the roots and operate on them. For example, in the last example we select the roots using Vieta’s theorem: the sum of the roots should be equal to 13 , and the product of the roots 36 . What are these numbers? Certainly, 4 and 9. Now calculate the sum of the square roots of these numbers: 2+3=5. That's it!

Division is defined as the inverse of multiplication.

To divide one number by another means to find a third number which, when multiplied by the divisor, will give the dividend in the product:

Based on this definition, we derive the division rule for rational numbers.

First of all, let us point out once and for all that the divisor cannot be zero. Division by zero is excluded for the same reason it was excluded in arithmetic.

The absolute value a is equal to the product of the absolute values ​​and c. This means that the absolute value of b is equal to the absolute value of a divided by the absolute value

Let us define the sign of the quotient s.

If the dividend and divisor have the same signs, then the quotient is a positive number. Indeed, if a and are positive, then the quotient o will also be a positive number.

Example. because

If a and are negative, then the quotient of c must also be positive in this case, since by multiplying by its negative number we must obtain a negative number a.

Example. because

If the dividend and divisor have different signs, then the quotient is a negative number. Indeed, if a is positive and a is negative, then c must be negative, since by multiplying a negative number by it we must obtain a positive number a.

Example. because

If a is negative and a is positive, then in this case c must be a negative number, since by multiplying a positive number by it we must obtain a negative number a.

Example. because

So, we came to the following division rule:

To divide one thing by another, you need to divide the absolute value of the dividend by the absolute value of the divisor and put a plus sign in front of the quotient, if the dividend and the divisor have the same signs, and a minus sign,

if the dividend and divisor have opposite signs.

As we have already said, division by zero is impossible, let us explain this in more detail. Suppose you need to divide some non-zero number, for example -3, by 0.

If the number a is the desired quotient, then by multiplying it by the divisor, that is, by 0, we must obtain the dividend, that is, - 3. But the product is equal to 0, and the dividend - 3 cannot be obtained. From this we conclude that the number

You can't divide 3 by zero.

Let the number 0 be divided by 0. Let a be the required quotient; multiplying a by the divisor 0, we obtain 0 in the product for any value of a:

Thus, we did not get any specific number: multiplying any number by 0, we get 0. Therefore, dividing zero by zero is also considered impossible.

For rational numbers, the following basic property of the quotient remains in force:

The quotient of two numbers will not change if the dividend and divisor are multiplied by the same number (not equal to zero).

Let us explain this with the following examples.

1. Consider the quotient, multiply the dividend and the divisor by - 4; then we get a new quotient

So, in the new quotient we got the same number 2.

2. Consider the quotient, multiply the dividend and the divisor by - then we get the following quotient:

The quotient has not changed since the result is the same number