There is a group of numbers: 1 * 2,2 * 3,3 * 4, ··········································································

n*（n+1）

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1. 1. 4 times the sum of a and 9 () 2. 30 less than 5 times of X () 3. The sum of X and Y divided by their difference () 4. The sum of a and its reciprocal () 5. The square of the sum of M and n ()
2. 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?
3. 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?
4. 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?
5. 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?
6. There is a column of numbers, which are arranged into 1, - 2,4, - 8,16, - 32 according to a certain rule, in which the appropriate number of three adjacent numbers is - 96, what are the three numbers?
7. A series of numbers arranged regularly are: 2, 3, 10, 15, 26, 35 According to this rule, what is the seventh number in this column?
8. Observe the following column: 1 / 2, - 1 / 6,1 / 12, - 1 / 20. Please find out the rule of arrangement and fill in the blanks according to the rule If n is an integer greater than 1, write the nth number according to the above arrangement
9. 1. Observe the following column number: - -. 2, 6, 12, 20. Please find out the rule of arrangement and fill in according to this rule 1 1 1 1 Look at the following number of columns: ---- 2 ， 6 ， 12 ， 20 Please find out the rule of arrangement and fill in the blanks according to the rule (1) The ninth number is___ The fourteenth number is. (2) If n is an integer greater than 1, write the nth number according to the above arrangement
10. Observe the following column of numbers: 1 / 2, - 1 / 6,1 / 12, - 1 / 20. Please find out the rule and fill in the blanks according to the rule. The ninth number is ()
11. Eighth grade mathematics: when the letters in the following formula meet what conditions, the fraction is meaningful~~~ 1. 2/a 2. x+1/x-1 3. 2m /3m+2 4. 1/x-y 5 2a+b/3a-b 6. 2/x-2 It's a process! Because of what, so what form
12. A series of numbers are arranged according to the following rules: 1, 2, 3, 2, 3, 4, 3, 4, 5, 4, 5, 5, 6, 6, 7 Ask for detailed explanation
13. There is a string of numbers, arranged in the following order: 1 / 2 - 1 / 3 2 / 3 - 1 / 4 2 / 4 - 3 / 4 1 / 5 - 2 / 5 3 / 5 - 4 / 5 There is a string of numbers, arranged in the following order: 1 / 2 - 1 / 3 2 / 3 - 1 / 4 2 / 4 - 3 / 4 1 / 5 - 2 / 5 3 / 5 - 4 / 5
14. According to a certain rule, arrange the number of the string: 1 / 1, 1 / 2, 2 / 2, 1 / 3, 2 / 3, 3 / 3, 1 / 4, 2 / 4, 3 / 4, 4 / 4.1/100, 2 / 100.. 100 / 100 Arrange the numbers according to a certain rule: 1 / 1, 1 / 2, 2 / 2, 1 / 3, 2 / 3, 3 / 3, 1 / 4, 2 / 4, 3 / 4, 4 / 4.1/100, 2 / 100, 3 / 100.. 99 / 100, 100 / 100. Please calculate the sum of these numbers?
15. A series of numbers are arranged according to the rule "1,2,3,2,3,4,3,4,5 ~ ~ what is the sum of the first 100 numbers?
16. There are a series of true scores, arranged according to the following rules: 1 / 2, 1 / 3, 2 / 3, 1 / 4 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 What is the 100th score?
17. Arrange the positive integers as follows: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. What's the 25th number on line 100? one 2、3 4、5、6 7、8、9、10 11、12、13、14、15
18. A series of numbers are arranged according to the following rule: 1,3,5,2,4,6,3,5,7,4,6,8,5,7,9... From the first number, what is the sum of the first 100 numbers?
19. 1,3/4,2/3,5/8,3/5,…… According to a certain rule, find the 100th number___
20. Here is a set of numbers arranged regularly: 1,3 / 4,2 / 3,5 / 8,3 / 5