Observe the following number: 1 2，3 4，5 6，7 8，… Then the k-th number of this group is______ .

Observe the following number: 1 2，3 4，5 6，7 8，… Then the k-th number of this group is______ .

Because the molecular rule is 2k-1, and the denominator is 2K,
So the k-th number should be 2K − 1
2k．

Here is a set of regular numbers: 1, - 2,4, - 8,16,..., what should be the 2009 number?

Here is a set of regular numbers: 1, - 2,4, - 8,16,..., what should be the 2009 number?
(-2)^(n-1)=2^2008

Observe the order of a group of numbers: 1,2,3,4,3,2,1,2,3,4,3,2,1 So, what's the number of 2009? A.1 B.2 C.3 D.4 It's better to elaborate on why

If you choose C, the rule is 123432. If you divide 2009 by 6, you will get 334334 times 6 to get 2004. Therefore, starting from 2005, 123432 gets 2009 as 3

Observe the following numbers: - 1 / 2,2 / 3, - 3 / 4,4 / 5, - 5 / 6 According to their arrangement rules, we know that the 2009 number is?

-2009/2010
First of all, the odd numbers are negative. The numerator is just a few, and the numerator is one less than the denominator,

The following set of numbers 2,4,6,8,10 The number of 2009 should be____________ .

The expression of the nth term of this sequence: 2n
So the number of 2009 = 2009 * 2 = 4018

Here is a list of regular numbers: 1, - 2,4, - 8,16 ···, what should be the 2010 number?

This is an equal ratio sequence with - 2 as the common ratio. The general formula is an = (- 2) ^ (n-1)
So the number of 2010 is (- 2) ^ 2009

A group of numbers 1, - 3,5, - 7,9 are given Please write the seventh number according to the rule______ The nth number is______ .

The first number is: (2 × 1-1) × (- 1) 2 = 1;
The second number is: (2 × 2-1) × (- 1) 3 = - 3;
The third number is: (2 × 3-1) × (- 1) 4 = 5;
And so on
The seventh number is: (2 × 7-1) × (- 1) 8 = 13;
The nth number is: (2n-1) × (- 1) n + 1 = (- 1) n + 1 (2n-1)
Therefore, 13 and (- 1) n + 1 (2n-1) should be filled in

Find out the arrangement rule of (1,3,5) (2,6,10) (3,9,15) (4,12,20). The three numbers of group 8 are respectively (), and the three numbers of group n are respectively

（8,24,40） （n,3n,5n)

According to (1, 2, 3), (2, 4, 6), (3, 6, 9), (4, 8, 12) Write the three numbers in the tenth group

The first number in the tenth group is 10,
10×2=20；
10×3=30；
So this set of numbers is: (10, 20, 30)

According to (1, 2, 3), (2, 4, 6), (3, 6, 9), (4, 8, 12) Write the three numbers in the tenth group

The first number in the tenth group is 10,
10×2=20；
10×3=30；
So this set of numbers is: (10, 20, 30)