The electric fan is not an electric heater, it mainly converts electrical energy into mechanical energy (only a small amount of electrical energy into heat), q (heat) () W

Electric fan is not electric heater, it mainly converts electrical energy into mechanical energy (only a small amount of electrical energy into heat), q (heat) (less than) W

The price of a set of desks and chairs is 60 yuan, of which the price of a chair is five seventh of that of a desk. How much is the price of a chair?
1. Xiao Dong read a book. He read 23% of the whole book on the first day and 31% of the whole book on the second day. He read 108 pages in two days. How many books does this book have?
two
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The price of a set of desks and chairs is 60 yuan, of which the price of a chair is five seventh of that of a desk. How much is the price of a chair?
[60 ÷ (1 + 5 / 7)] × 5 / 7 = 25 (yuan)
Xiao Dong read a book. On the first day, he read 23% of the whole book. On the second day, he read 31% of the whole book. In two days, he read 108 pages. How many books does this book have?
108 ÷ (23% + 31%) = 200 (pages)

What is the definition of monotone bounded sequence with only one limit?

If there is an upper bound, then there must be a supremum. The limit is defined as a supremum
If there is a lower bound, then there must be a infimum. The limit is defined as infimum

The boundedness of convergent sequence. What does boundedness mean?

The boundedness of convergent sequence means that the range of any term has upper and lower bounds
That is to say, the value of any term of the sequence is always between two finite constants!

The definition of bounded sequence and sequence {1,1 / 2,1 / 3,1 / N}
The definition of bounded sequence: for all N, there is xn ≤ m, where m is a constant independent of N. it is said that the sequence {xn} is bounded (with upper bound) and that M is one of its upper bounds
For all N, xn ≥ m, where m is a constant independent of N, it is called the lower bound of the sequence {xn} and M is called one of its lower bounds
But the sequence 1 / N is only less than 0, it is not less than or equal to a number, why is it a bounded sequence

First of all, your sentence "sequence 1 / N is only less than 0" is wrong. It should be greater than 0. In addition, the sequence an = 1 / N obviously satisfies 0

Special sequence
See a chart: 1
2 3
4 5 6
7 8 9 10
.
Count 1000 in the first few lines, why? How to ask? Who can be more detailed

In fact, it's very simple. You take 1, 2, 3... These numbers as some apples. Ha ha. One in the first row
Two in the second row. It's exactly the same as the graph. Then where is the 1000th apple?
You know the arithmetic sequence. 1,2,3,4····
The expression of the sum of this sequence is n (n + 1) / 2
Then you take in the number and find one close to 1000. When n = 44. N (n + 1) / 2 = 990
N=45.n(n+1)/2=1035
The 1000th apple must be in the 44th row
That's it. Thank you for your points

A very special sequence of numbers
1,3,16,45,121,320,841,2205,5776,15125...
Find a general formula
Next to geek, I think another foreign website is dedicated to special sequences
If you know the address
The above two problems can be solved by a positive solution

1^2 3 4^2 45 11^2 320 29^2 2205 76^2 15125
1 4 11 29 76
[a(n-1)]^3-a(n-2)=an
3,45,320,2205,15125
45=5^1*3^2
320=5^1*8^2
2205=5^1*21^2
15125=5^1*55^2
5*(an-an-1)^2
We can see some rules

Sum of special sequence
Sum:
(1) 1 + (1+2) + (1+2+2^2) + (1+2+2^2+2^3) + ...+ (1+2+2^2+...+2^n)
(n belongs to the set of positive natural numbers)
(2) 1/(1^2+4) + 1/(2^2+4) + ...+ 1/(n^2+2n)

1. Let Sn = 1 + (1 + 2) + (1 + 2 + 2 ^ 2) + (1 + 2 + 2 ^ 2 + 2 ^ 3) +... + (1 + 2 + 2 ^ 2 +... + 2 ^ n), then Sn = 1 * (n + 1) + 2 * (n) + 2 ^ 2 * (n-1) + 2 ^ 3 * (n-2) + +2^(n-1)*2+2^n*12Sn= 2*(n+1)+2^2*(n)+2^3*(n-1)+… +2^(n)*2+2^(n+1)*12Sn-Sn=-(n+1)+2+2^2...

The number set a satisfies: if a ∈ a, then 1 / 1-A ∈ a, (a ≠ 1). It is proved that the set a has at most three elements, and their sum is 1
Wrong number, should be; and their product is - 1

Proof
From the meaning of the title,
If a ∈ a, then 1 / 1-A ∈ a,
So a ∈ a, 1 / 1-A ∈ a,
And because 1 / 1-A ∈ a,
So 1 / (1-1 / (1-A)) ∈ a,
That is, (A-1) / a ∈ a,
That is 1 / (1 - (A-1) / a) ∈ a,
The reduction is a ∈ a,
So set a has at most three elements
They are a, 1 / (1-A), (A-1) / a respectively
And their product is - 1

Let a be a set of numbers and satisfy the following conditions: if P belongs to a and P is not 1, then 1 / 2 of (1-p) belongs to A. It is proved that there are at least three different elements in a set
Exercises of lesson 1 in senior one

Let me answer
According to the title
If P belongs to a and P is not 1, then 1 / 2 of (1-p) belongs to a
If 1 / 1 of (1-p) belongs to a, let 1 / 1 of (1-p) be x, then 1 / 1 of (1-x) belongs to a (because it is difficult to input, the specific formula will not be written)
If 1 / 1 of (1-x) belongs to a, let 1 / 1 of (1-x) be y, then 1 / 1 of (1-y) belongs to a, then 1 / 1 of (1-y) can be reduced to P,
So there are at least three elements P, X and Y in set a

The electric fan is not an electric heater, it mainly converts electrical energy into mechanical energy (only a small amount of electrical energy into heat), q (heat) () W