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Look at the following column of numbers: 1 / 2, - 1 / 6,1 / 12, - 1 / 20. Please find out the rule of arrangement and fill in the blanks according to the rule. The ninth number is the first
（-1）^(n+1)*1/(n*(n+1））
Let's have a formula
RELATED INFORMATIONS
- 1. Look at the following column of numbers in turn. Please write down the following three numbers. Can you point out what the number 2008 is? Look at the following column of numbers in turn. Please write down the following three numbers. Can you point out what the number 2008 is? 3,2,1,0, - 1, - 2, - 3,... 2008 1, - 1 / 2,2 / 3, - 3 / 4,4 / 5, - 5 / 6,... 2008 1, - 3,9, - 27,81, - 243... Then the nth number is
- 2. Look at the numbers in the following column. Please write down the following three numbers. Can you name the 10th number, the 101st number and the 2004 number? The first question: - 1, - 2, + 3, - 4, - 5, + 6, - 7, - 8, (), (), (). The second question: - 1, half, - 3, quarter, - 5, one sixth, - 7, one eighth
- 3. Observe the number of the following column in order, according to its arrangement. Please write the following three numbers and the nth number (1) 1,3,5,7,9, (), (), (). The nth number is () (2) 3,5,7,9,11, (), (), (). The nth number is () (3) - 3, - 1,1,3,5, (), (), (), the nth number is () (4) 5,3,1, - 1, - 3, (), (), (). The nth number is ()
- 4. There is a column of numbers; 25 8 11 14 in order, what is the 1995 number?
- 5. Q: a column number - 2, - 5, - 8, - 11, - 14 What is the 100th number?
- 6. There is a column of numbers: 2, 5, 8, 11, 14, * * *. The seventh number is 20. What should the number 2008 be and what should the number n be It's a seventh grade math problem
- 7. According to the law, fill in the appropriate number 54 / 5, 18 / 5, 6 / 5, 2 / 5 () in the brackets. Why
- 8. 2, 6, 18, 54, 162, -- -- what do you want to fill in the next two numbers?
- 9. Fill in the brackets with 3, 6, 18 and 54, and each number can only be used once, () △ () × () = ()
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- 11. Two fifths of a number is 25. What's half of the number
- 12. The sum of a and B is 800. Two fifths of B is 50 more than half of A. what is a and B
- 13. Two fifths of a number is three less than one half of it. What's the number?
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- 15. There is a column of numbers 1 / 2, 4 / 17. Then the eighth number is -------
- 16. 1.3.7.13.21.31 find the rule and express it with algebraic formula
- 17. In the algebraic formula: - 2x, Wu Fen a, B Fen a ten 1, 3 fen 1 (x ten y), n Fen 2 (m-2), 5 fen a ten B, there are () A.3 b.4 C.5 d.6 integers
- 18. The nth number of 1,5,9,13,17 is expressed by algebraic formula
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