Arrange the positive integers as follows: 1 23 4 5 6 7 8 9 10 Q: what's the 25th digit in line 100 First line, 1 Second line, 23 Shanxing, 456 The fourth line, 789 10 The fifth line······

This is the summation of arithmetic sequence. The nth digit in the lower m row should be m (m-1) / 2 + n. m (m-1) / 2 is the number of digits in the first M-1 row
The 25th value in line 100 is 100 * (100-1) / 2 + 25 = 4975

There are a series of true fractions, arranged according to the following rule: 1 / 2, 1 / 3, 2 / 3, 1 / 4 What is the 100th score?
There are a series of true fractions, arranged according to the following rules: 1 / 2, 1 / 3, 2 / 3, 1 / 4, 2 / 4, 3 / 4, 1 / 5, 2 / 5, 3 / 5, 4 / 5 What is the 100th score?

The score of the string is one positive and one negative, so we can infer that the 100th is a negative number, one with denominator 2, two with denominator 3, and three with denominator 4 And so on 1 + 2 + 3 + 4 + 5 + 6 + +13=911+2+3+4+5+6+…… +14 = 105 molecules have 14 numbers, the denominator is 15, the 105th fraction is 14 out of 15, the sixth from the bottom

When the letters in the following formula meet what conditions, the fraction is meaningful?
1.a/1
2.x^2-4/3
3.x^2+4/3
4.x-2y/x+xy
Known fraction x + 2 / x ^ 2-4
(1) When what is the value of X, the fraction is meaningless?
(2) When what is the value of X, is the fraction meaningful?
(3) When what is the value of X, the fractional value is 0?

The so-called meaningful is that the denominator of the fraction is not zero

YNGYBNP
* P
___________
PAXHEBY

1041809
* 9
________
nine million three hundred and seventy-six thousand two hundred and eighty-one
y=1 n=0 g=4 b=8 p=9 a=3 x=7 h=6 e=2

If the following formula makes sense, find the value range of the letter
(1) Radical 3-x
(2) Root 2x-1 / 5
(3) Root of X 1-x
(4) Root x + 3 + root 8-x
(5) Radical X-2 + radical 2-x
(6) Radical X & # 178; - 2x + 1

（1）3-x≥0,x≤3
（2）2x-1/5≥0,x≥1/10
(3) X ≠ 0 and 1-x ≥ 0, X ≤ 1 and X ≠ 0
(4) X + 3 ≥ 0 and 8-x ≥ 0, - 3 ≤ x ≤ 8
(5) X-2 ≥ 0 and 2-x ≥ 0, x = 2
(6) X is r

The meaning of letters in Mathematics
Z. What numbers do n, Q and R represent respectively? If there is an asterisk on N, what does it mean?

Z represents the set of integers in the set
N represents the set of natural numbers in a set
Q stands for the set of rational numbers
R stands for the set of real numbers
N * or Z + represents a set of positive integers

In the range of real numbers, what is the value of the letter?
1. (5-x under root)
2. (x under radical) - 1 / 1
3. X-2 under root

1.x

The number of columns in regular order: 2, - 4, 8, - 16, 32, - 64 The sum of some four adjacent numbers is - 640. What is the difference between the largest number and the smallest number?

Let the first of the four adjacent numbers be x, then the last three numbers are - 2x, 4x, and - 8x in turn. From the meaning of the question, we can get: x-2x + 4x-8x = - 640, and the solution is: x = 128. Then - 2x = - 256, 4x = 512, and - 8x = - 1024. ｜ 512 - (- 1024) = 1536

The number of columns in regular order: 2, - 4, 8, - 16, 32, - 64 The sum of some four adjacent numbers is - 640. What is the difference between the largest number and the smallest number?

Arrange the positive integers as follows: 1 23 4 5 6 7 8 9 10 Q: what's the 25th digit in line 100 First line, 1 Second line, 23 Shanxing, 456 The fourth line, 789 10 The fifth line······