What is Integer: Definition and 620 Discussions

An integer (from the Latin integer meaning "whole") is colloquially defined as a number that can be written without a fractional component. For example, 21, 4, 0, and −2048 are integers, while 9.75, 5+1/2, and √2 are not.
The set of integers consists of zero (0), the positive natural numbers (1, 2, 3, ...), also called whole numbers or counting numbers, and their additive inverses (the negative integers, i.e., −1, −2, −3, ...). The set of integers is often denoted by the boldface (Z) or blackboard bold



(

Z

)


{\displaystyle (\mathbb {Z} )}
letter "Z"—standing originally for the German word Zahlen ("numbers").ℤ is a subset of the set of all rational numbers ℚ, which in turn is a subset of the real numbers ℝ. Like the natural numbers, ℤ is countably infinite.
The integers form the smallest group and the smallest ring containing the natural numbers. In algebraic number theory, the integers are sometimes qualified as rational integers to distinguish them from the more general algebraic integers. In fact, (rational) integers are algebraic integers that are also rational numbers.

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  1. M

    Proving Properties of z When n is Odd/Even Integer

    Homework Statement if z = 1/sqrt 2 + i/sqrt2 Homework Equations show that z + z4n+1 = 0, when n is any odd integer. if n is an even integer, find z + z4n+1 in rectangular form. The Attempt at a Solution I have no clue where to start...
  2. I

    The integer part is (? distributive ?)

    the integer part is ... (?? distributive ??) Homework Statement Define the floor of a real number k where [k] is the least smallest integer from k. I want to show that [a - b] = [a] - [b] Homework Equations n/a The Attempt at a Solution [1.2 - 5.7] = [-3.8] = -4 [1.2] - [5.7]...
  3. M

    Solving Switch Statement Problem with y as Integer

    Homework Statement switch statements. y is an integer number. Use a switch statement to set B equal to one of the following values: true, false, or the vector [1 0 1]. If y is {1,2,3,5,7}, then set B to true. If y is {4, 6, 8, 10}, then set B to false. If y is neither, then set B to the...
  4. B

    Prove that the inverse of an integer matrix is also an integer matrix

    Homework Statement A is an invertible integer matrix. Prove that if det A = 1 or det A = -1, then the inverse of A is also an integer matrix. Also prove the reverse, if A-inverse is an integer matrix then its determinant is 1 or -1. Homework Equations I'm not too sure how to start...
  5. H

    Why 30 is the largest integer such that none of its ?

    Why 30 is the largest integer such that none of its...? Why 30 is the largest integer such that none of its totatives are composite? which means All the coprime numbers that below 30 are primes.. 30=> 7,11,13,17,19,23,29 ?// and if you have a proof that it is the biggest integer please Help...
  6. D

    Proving 3 Divides at Least One Integer

    Homework Statement Prove that 3 divides one of the integers n, n + 2, or n + 4, for any integer n. Homework Equations The Attempt at a Solution
  7. Ed Aboud

    Prove Integer Expression: a(a^2 + a)/3 is an Integer

    Homework Statement Prove that the expression \frac{a(a^2 + a)}{3} is an integer for all integers \geq 1 Homework Equations The Attempt at a Solution a(a^2 + a ) = 3q + r r can be: r = 0,1,2 for r = 0 \frac{a(a^2 + a)}{3} = q q is an integer by the division algorithm. When I...
  8. K

    Summed exponents for a 8- digit positive decimal integer

    ABCDEFGF is an 8-digit positive decimal integer, where each letter represents a different decimal digit from 0 to 9. The digits 1 and 9 do not appear. The nonzero even digits appear in ascending order, and the odd digits appear in descending order in ABCDEFGF. None of A and E can be zero...
  9. K

    Some Summed Digits In A 9-Digit Positive Integer

    Determine a 9-digit positive integer that uses each of the decimal digits from 1 to 9 exactly once, such that: (i) The sum of the digits 1 and 2 and all the digits between them is 9. (ii) The sum of the digits 2 and 3 and all the digits between them is 20. (iii) The sum of the digits 3...
  10. T

    For integer x only, is x considered a polynomial?

    For integer x only, is x! considered a polynomial?
  11. M

    Proving that a^2-2b^2-4c^2 = 0 has no positive integer solutions

    so I have to prove that a^3-2b^3-4c^3 = 0 has no positive integer solutions. I have gotten through most of the proof but now I am stuck, and if you guys could give me a nudge in the right direction that would be great. work done so far: proof by contradiction, i assumed that...
  12. S

    Every integer can be written as a sum of a square and square free integer

    Homework Statement show that every positive integer can be written as the product of a square and a square-free integer (an integer that is not divisible by any perfect squares other than one The Attempt at a Solution well i can see by example that this works: i.e 60=22*3*5...
  13. T

    Solving for the Largest Positive Integer n

    Homework Statement Find the largest positive integer n such that n^3 + 100 is divisible by n + 10. Homework Equations The Attempt at a Solution The hint I've been given is to use (mod n + 10) to get rid of the n. but i don't quite see how it would work :S all my attempts...
  14. P

    Modular Congruences of Integer Squares

    prove that for any integer n, n^{2} \cong 0 or 1 (mod 3), and n^{2} \cong 0,1,4(mod 5)
  15. B

    Invertible Matrices with det=1 & Integer Entries: Why Inverse is Integer?

    Can someone explain why if an invertible matrix A has det = 1 and all integer entries, its inverse also has all integer entries? det(A) = 1 means that if you apply the big formula (permutations) the sums of the entries add up to 1. But what does that have to with having integers in its...
  16. hxtasy

    How would you mathematically describe an integer?

    For example a number whose domain would be all positive would be described as a number k, where k > 0. How would you describe a number that is an integer, ie not 1.4, 7.666 et cetera. I can't think of a way to define this mathematically (or a way that includes any number of digits). I know...
  17. S

    C/C++ (C++) How would I display a value rounded to the nearest integer?

    Like for example Prompting message reads. "Please enter a positive value" Example: Please enter a positive value: 234.7 Rounded to the nearest integer the number is: 235 Please enter a positive value: 10.3 Rounded to the nearest integer the number is: 10 What I have...
  18. T

    Proving Every Integer > 11 is Sum of Two Composite Numbers

    Homework Statement Use proof by contradiction to show that every integer greater than 11 is a sum of two composite numbers. The Attempt at a Solution The question sounds a bit awkward for me since for the numbers I have tested so far. The number can be consists of 1 prime 1 composite or...
  19. S

    Plot of greatest integer fuction

    I was given this homework today and without much explanation from the teacher , I can't find anything similar in my book, 1.- [[ x]] = [[y]] find outside domain/range , argue inclusion or exclusion 2.- compare and contrast (1) y=[[2x]] (2) y=2[[x]] (3) y= [[x/2]] 3.- state domain and...
  20. S

    Problem in integer declaration

    Dear all, I have a problem with Fortran 90. I want to declare an integer which is enable to support till numbers such as Avogadro number (6.022*10**23). I use "Microsoft Fortran PowerStation 4.0". Can anyone can help me please? Regards,
  21. A

    Electric Flux: Is it an Integer or a Real Value?

    I have a doubt about electric flux. It is said to be the no. of field lines passing through a given area. But then we integrate it as: \int\vec{E}.\vec{ds}=\Phi However, bein the number of field lines does it not have to be an integer?
  22. L

    Find lim (-1)^[x] x->2 [x] is the greatest integer function

    find lim (-1)^[x] x->2 [x] is the greatest integer function -> means tends to thanks to any help.
  23. V

    Integer Factorization Algorithm

    I am posting an integer factorization algorithm that I have developed. I am hoping for feedback on any obvious flaws that I might have missed before writing a computer programme to test it out. Thanks in advance Visu
  24. S

    MATLAB Solving an integer with FFT in matlab

    Homework Statement Hi, I hope someone could help me, I have been trying to solve this problem with FFT in matlab, why?, because my teacher gave it as homework. The problem is the following. Obtain the value of the following integer using FFT: Homework Equations the integer goes...
  25. S

    MATLAB Finding an integer with matlab fft function

    Hi, I hope someone could help me, I have been trying to solve this problem with FFT in matlab, why?, because my teacher gave it as homework. The problem is the following. Obtain the value of the following integer using FFT: the integer goes from [-infinte, infinite], and the function is...
  26. M

    How Can You Maximize the Product of Integers Given a Fixed Sum?

    we must obtain 'N' and a(i) i=1,2,3,....,N on condition that the product a(1)a(2)a(3)...a(N) is the highest possible a(1)+a(2)+a(3)+...+a(N)=73 every a(i) is positive here N (this is the hardest part) is not known and must be calculated
  27. quasar987

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  28. D

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  29. C

    Proving Existence of Integer y and z for x in Positive Integers

    Homework Statement Prove that for all x there exists and x if it is an element of the positive integers, then there is an integer y and an integer z. Homework Equations The Attempt at a Solution I know that the contrapositive would be "If there is not an element of the positive...
  30. Y

    Invertible Elements in Zn and Factoring over Z[i]

    Homework Statement Can someone explain the notation of the integer ring(Z)? My friend's in Math 100 and has questions on Z. I have never heard of ring's before and I'm at a loss to help him. From what I've gathered Z is a set of all integers. They ask for the invertible elements in different...
  31. M

    How Do You Solve Linear Diophantine Equations?

    Homework Statement I don't know where to start on this question - could someone please point me in the right direction so i can look up the method. Q: Find integers x, y such that 45x + 63y = 99. Can we find integers s, t such that 45s +65t = 80? Either find them or prove they cannot exist.
  32. G

    Is there a relationship between remainders and positive integers?

    let n be a-positive integer. Prove that a and c leave the same remainder if and only if a - c =nk for some integer k.
  33. J

    (Proof) Square of integer is 3k or 3k+1

    Homework Statement Prove that the square of any integer a is either of the form 3k or of the form 3k+1 for some integer k.Homework Equations The Division Algorithm: Let a,b be integers with b>0. Then there exists unique integers q and r such that a = bq + r and 0<=r<bThe Attempt at a Solution...
  34. S

    Exploring the Non-Integral Solutions of the Greatest Integer Function

    can anyone tell me how to solve for integer solutions of [x]*[y]=x+y tell the interval of its non integral solutions pleazzzzzzzzzzzzzzzzzz...
  35. B

    Integer solutions for equations A * [(B + C)(D - E) - F(G*H) ] / J = 1

    Could anyone please answer this You are confronted with the following formula: A * [(B + C)(D - E) - F(G*H) ] / J = 10 Knowing that each variable is a unique, single-digit, nonzero number, and that C - B = 1, and H - G = 3, what is the number ABCDEFGHJ, where each letter is a digit...
  36. Q

    Finding Integer Solutions for y^2 = x^3 + n

    how does one go about finding integer solutions for an equation such as this? Is it easier to merely find how many solutions? y^2 = x^3 + n, n is some integer.
  37. D

    Solving X^4+131=3y^4: No Integer Solutions

    This is a problem from Terence Tao's book, and I cannot locate the solution anywhere, so I thought I'd post it here. 1. Homework Statement X^4+131=3y^4, Show that the equation has no solutions when x and y are integers. Homework Equations None? Not sure. The Attempt at a...
  38. E

    Proving C(n,m) is an Integer: Number Theory & Chinese Remainder Theorem?

    Homework Statement How would you prove using number theory that C(n,m) is an integer where n => m =>1? Do you need the Chinese Remainder Theorem? It seems like it should follow easily from what C(n,m) represents but it is hard for me for some reason. Homework Equations The Attempt...
  39. T

    Help Solve the Maths Challenge: Positive Integer with All Digits 1

    one of the "maths challenge" questions. one of the only ones i couldn't do :S I've tried for a good number of hours, but havnt found a way to do it. I feel any more time would just be brute forcing it which i wouldn't have time for in the exam anyways. hope you can help Homework Statement...
  40. C

    Are There Integer Eigenvalues for a Specific Matrix?

    Homework Statement I need the eigenvalues of [[3, -1][-1, 1]] (ie [[row1][row2]]) The Attempt at a Solution A-xI = [[3-x, -1][-1, 1-x]] so I get the characteristic polynomial x^2-4x+2=0 from det(A-xI)=0 Is this correct? Because I won't get integer eigenvalues from it
  41. S

    Analysis - irrational number or positive integer

    Homework Statement Let n and k be positive integers. Show that k^{1/n} is either a positive integer or an irrational number. The Attempt at a Solution I set q = k^{1/n}. Then I set q = \frac{m}{p} . (Where m and p don't have common factors.) Then m^n = k * p^n . So then k is a factor...
  42. cepheid

    What is the Divisibility Rule for the Reflection of an Integer?

    "Reflection of an Integer" I haven't encountered this before. I'm not sure how to approach it. At this point it's not even clear to me why the result should only be divisible by one number in *every* case. The reflection of a positive integer is obtained by reversing its digits. For...
  43. P

    Polynomials do or don't have integer roots?

    Homework Statement Is it there a method to find out if a polynomial has no integer roots? The Attempt at a Solution I tried the division of polynomials, as well as the Horner's Method, but no luck.
  44. K

    Counting Integer Roots of a Polynomial Using Sturm Sequences

    Hi,.. using a Sturm or other sequence, could we find how many integer roots have the Polynomial K(x)= \sum_{n=0}^{d} a_{n}x^{n} where all the 'a_n' are integers (either positive or negative)
  45. K

    Counting Integer Solutions to Curves of the Form x^n-c-ky=0

    Let be a open curve on R^2 so x^{n}-c-ky=0 where k,n and c are integers, are there any methods to calculate or at least know if the curve above will have integer roots (a,b) so a^{n}-c-kb=0 ?? or perhaps to calculate the number of solutions as a sum (involving floor function) over integers of...
  46. S

    Atomic Weights: Why They're Not Integer & What is an AMU?

    Why are the atomic weights of elements not integers and how many grams would there be in 1 amu (atomic mass unit) of a material? I know these are trivial questions but it's been a long time since I left school! Thanks. -SK
  47. D

    What is the best method for finding integer solutions to a challenging function?

    Is there a quick way to find integer values of x that give integer values for y? (x^2-R)/(P-2x)=y sqrt(R) rounded down<x<P/2 an equivalent equation is x^2+Px+R=y y= a perfect square sqrt(x^2+Px+R)= integer P and R are integer values. They are very large...
  48. D

    Proving m + 1/m = Integer When m = 1

    Homework Statement Prove that if m is a positive rational number, then: m + 1/m = integer Only when m = 1 Homework Equations Don't know any The Attempt at a Solution That's the problem, I don't know where to start. I have tryed a few things, but none of them works out for...
  49. K

    An Integer Temperature Puzzle

    The other day, Mack was preparing a table consisting of integer Fahrenheit temperatures (F) which yields integer Celsius (C) equivalent upon conversion. He noted that F= 527 gave the corresponding C value as 275 and realized that, he could have simply moved the first digit in F to the end to...
  50. A

    An integer between n and n+1 where n is an integer.

    hi guys.. Does this statement require a proof? It seems pretty obvious to me. "prove that there is no integer between n and n+1 where n is an integer." Also if it does require a proof, what I need to show? Just few hints will suffice. thanks jitendra
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