What does comma mean in mathematics? For example, use a comma to connect two intervals (negative infinity, 0), (0, positive infinity) Is this "and" or "or something

What does comma mean in mathematics? For example, use a comma to connect two intervals (negative infinity, 0), (0, positive infinity) Is this "and" or "or something

It should be "harmony" and cannot be understood as "union"

What does a comma mean?
In one sentence: A, B is C
Is it correct to understand a as C or B as C?
Urgent need

Is a C or B C

Comma means, I need it urgently!

Commas are used between coordinate components, such as subject, predicate, predicative, object and adverbial. If there are only two coordinate components and there are conjunctions, they are no longer connected by commas. However, among three or more coordinate components, except the last two are connected by conjunctions, the rest are separated by commas
There is a pause and a comma in the middle of each sentence
There are no more than three types of pauses represented by commas
One is the pause between clauses,
The second is to express the pause between the elements in the sentence,
The third is to express the pause within the sentence elements;

If one side of the parallelogram ABCD is ab = 9, diagonal AC = 12, BD = 6, root 5, then the perimeter of the parallelogram ABCD is________ .

Let BD and AC intersect point o
Then Bo = 3, radical 5, Ao = 6,
According to Pythagorean theorem, ABO is a right triangle
So the quadrilateral ABCD is a diamond
The perimeter is 4x9 = 36

Solving equation 6 * 25 ^ x = 9 ^ x + 15 ^ x

6*25^x = 9^x + 15^x
6*5^(2x) = 3^(2x) + 3^x*5^x
6 * 5 ^ X / 3 ^ x = 3 ^ X / 5 ^ x + 1, divide up and down by 3 ^ x * 5 ^ x, ∵ 15 ^ x ≠ 0
6*(5/3)^x = (3/5)^x + 1
6 = (3/5)^x/(5/3)^x + (3/5)^x
(3/5)^(2x) + (3/5)^x - 6 = 0
Let u = (3 / 5) ^ X
u² + u - 6 = 0
(u-2)(u+3) = 0
u = 2 or u = -3
(3 / 5) ^ x = 2 or (3 / 5) ^ x = - 3, (rounding)
x = log2/log(3/5)
=log2 / (log3 - log5)

If the symmetry axis of the ellipse is the coordinate axis, the sum of the length of the major axis and the length of the minor axis is 18, and the focal length is 6, then the equation of the ellipse is ⊙___ ．

Let the major and minor half axes of the ellipse be a and B respectively, then 2 (a + b) = 18, that is, a + B = 9, ①, from the focal length of 6, we get C = 3, then A2-B2 = C2 = 9, ②, from ① we get a = 9-b, ③ into ②, we get: (9-b) 2-b2 = 9, simplify to 81-18b = 9, we get b = 4, and B = 4 into ①, we get a = 5, so the ellipse

14 is a positive number, a fraction, and a rational number. 0 is neither positive nor negative, but the integer is - 2

Incorrect is that: - 3.14 is a positive number, fraction is also a rational number [- 3.14 is a negative number]

Find the domain of definition: (1) y = x & # 178; - 2x-3 (2) y = 1 / X-5 (3) y = root 3x & # 178; + 2x-1

Solution
1) Y = x & # 178; - 2x-3 is defined as R
2) Y = / (X-5) denominator cannot be 0
So X-5 ≠ 0, X ≠ 5
3）Y=√3X^2+2X-1
3X^2+2X-1>=0
(3X-1)(X+1)>=0
10> = 1 / 3 or X

The difference between the reciprocal of - 8 and the product of 2 is equal to?

The inverse of 1 / 2 is - 1 / 2, and the reciprocal of - 8 is - 1 / 8
（－1／2）×1／4－［（－1／8）×2］
＝－1／8－（－1／4）
＝－1／8＋1／4
＝－1／8＋2／8
＝1／8
A: the difference between the reciprocal of - 8 and the product of 2 equals 1 / 8

Solving the equations: x + y = 7Y + Z = 8Z + x = 9

(1) The solution of the original inequality system is x = 4Y = 3Z = 5