What is the definition of accuracy?

What is the definition of accuracy?

Accuracy refers to the close degree between the measured results and the true values. Precision refers to the reproducibility between the results obtained by repeated determination with the same kind of spare sample. High accuracy of measurement means that the system error is small, when the average value of the measured data deviates from the true value

Approximate values 4.0 and 4 are equal in size and accuracy______ (judge right or wrong)

4.0 = 4, so 4.0 and 4 are the same size; 4.0 means accurate to one tenth, 4 means accurate to 1, so the accuracy is different

Approximate values 8 and 8.0 represent the same accuracy

No

How to prove that algebraic numbers are countable?
Such as the title, but also forget the expert advice
Can you give me more details? How to prove it?

The idea of proof: 1. The roots of integral coefficient polynomials are less than or equal to the power of polynomials in the complex range, that is, they can be counted at most. Basic principles of algebra. 2. All integral coefficient polynomials are countable sets. This step is very easy. 3. Combined with 1 and 2, the algebraic number set belongs to the Union (countable set) of all solution sets of integral coefficient polynomials

How to prove that this number is an algebraic number
It's not very easy to input, please see this picture

The number you give can be reduced to (1 + radical 5) / 4,
It is easy to know that it is a root of the quadratic integral coefficient algebraic equation: 4x2-2x-1 = 0
According to the definition of algebraic number: algebraic number is to satisfy the form of anxn + an-1xn-1 + The real number or complex number of an algebraic equation with integral coefficients of degree n of one variable (n ≥ 1, an ≠ 0) + a 1 x + a 0 = 0, of course, this number is an algebraic number

Please analyze and prove that there are as many rational numbers as natural numbers

Rational numbers can be arranged in a certain order as follows
0,1/2,1/3,2/3,1/4,2/4,3/4,1/5,2/5,3/5,……
Remove the duplicate, such as 2 / 4 (because 2 / 4 = 1 / 2)
In this way, all rational numbers are arranged into a series of numbers in a certain order, so rational numbers and natural numbers are one-to-one corresponding, so rational numbers are as many as natural numbers, they are countable sets, and the cardinality is the same

How to prove that natural number set and rational number set have the same number

P / Q is represented by (P, q) (1,n) … (2,1) (2,2) (2,3) (2,4) … (2,n) … … … … (m,1) (m,2) (m,3) (m,4) … (m,n) … In this way, the set of rational numbers is an ordered set (countable set)

Let m and n be natural numbers, M > N, set a = {1,2,3 , m}, set B = {1,2,3 , n}, the subset C of a satisfying B ∩ C ≠ & # 8709; is common____ individual
Let m and n be natural numbers, M > N, set a = {1,2,3 , m}, set B = {1,2,3 , n}, the subset C of a satisfying B ∩ C ≠ empty set is common____ One
2^m-2^(m-n)
Why?

There are 2 ^ m subsets of A. if the subset C of a satisfies B ∩ C = empty set, then the elements of C must not contain the elements of B, and the elements of a that are not contained in B have {n + 1, N,..., m}. There are M-N elements in total. The subsets formed by them must be disjoint with B, and the disjoint subsets of a must be in these subsets

Let set a and set B be set n of natural numbers, and map f: a → B maps element n in set a to element 2n + N in set B, then under map f, the original image of image 20 is______ ．

Let n = 0, 1, 2, 3, 4 So the answer is: 4

Given the set a {x [x = 3N times, n belongs to natural number}, B = {x [x = 3N, n belongs to natural number}, find the intersection and union of a and B

Let 3 ^ n be the nth power of 3, and 3 ^ 0 = 1
3^n=3*3^(n-1)=3m
That is to say, for any x ∈ a, there is x ∈ B
The element of B is not necessarily the element of a, such as 6 ∈ B, but it can not be expressed as 3 ^ n, 6 is not included in a
So a is the proper subset of B
A∩B=A,A∪B=B