Look at the following sequence of numbers, one half minus one sixth minus one twelfth minus one twentieth... And so on, the ninth number is（

one-ninetieth

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1. Look at the following column: half, one sixth, one twelfth, one twentieth And so on, what are the ninth and fourteenth numbers? Why?
2. The number of columns arranged according to a certain rule is negative half, one sixth, one twelfth, one twentieth and one thirtieth According to this rule, the 99th number is ()
3. One half, one sixth, one twelfth, one twentieth, one thirtieth The 60th number is ()
4. Observe the rules and fill in the blanks: 1 and 1 / 2, 2 and 1 / 4, 3 and 1 / 8 The nth number is（
5. There is a group of numbers: 1, 2, 5, 10, 17, 26,..., please observe the law of the composition of this group of numbers, and use the law you found to determine the eighth number as____ The nth number is ()
6. What are the rules of 1,2,5,10,17,26 1, 2, 5, 10, 17, 26. What's the rule
7. There is a column of numbers 7, O, 2,5,3,7,0,2,5,3. What is the 19th number and the 28th number
8. There is a question, when a = 19 / 17, B = -0.198 Find the fourth power of the algebraic formula 41a - the third power of 7a, the second power of B - the second power of 5A, the fourth power of B - the fourth power of 29a + the second power of 4A, the second power of B + the third power of 5A, the second power of B - the fourth power of 12a + the second power of B, the second power of a + the second power of 2B, the third power of A. Wang Meng points out that the condition a = 19 / 17 (17 / 19), B = -0.198 given in the title is redundant. Do you think his statement is reasonable, why? 2. It is known that the quadratic power of p-pq = 1 and the quadratic power of pq-3q = 2 Finding the quadratic power of P + 3pq-3q The first question is more troublesome, please take paper to help me calculate
9. Number of columns 13.1, 15.1, 17.1, 19.1 387.1, the average of this column is ()
10. On the number axis, the number corresponding to point a is negative, and the number corresponding to point B is positive 17. Measure the distance between two points a and B
11. 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 ()
12. 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
13. 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
14. 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?
15. 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?
16. 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?
17. 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?
18. 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?
19. 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?
20. 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 ()