New year's calendar New year's calendar, if any, please send 100 ~ 120 words

New year's calendar New year's calendar, if any, please send 100 ~ 120 words

Looking at the calendar, I was surprised and regretted to shout: "new year is coming!"
The pace of time is in a hurry. In a twinkling of an eye, the twelfth new year is coming. Twelve is a sign of growth, but it takes away my childhood full of childish interest
In the new year, people should throw away the old things and welcome the new things. Life is a road. People have to go through the dangers to reach their own destination

During the Spring Festival, Xiao Ming and Xiao Ying visit Mr. Li in a special way

2-1=1
1×7＝7
7－2＝5
5×7＝35
35+1＝36

During the Spring Festival, Xiao Ming and Xiao Ying visit Mr. Li, who gives them sugar in a special way
During the Spring Festival, Xiao Ming and Xiao Ying visit Mr. Li. Mr. Li gives them a piece of sugar in a special way. Mr. Li first gives him one seventh of the sugar left in the sugar box, then gives Xiaoying two pieces of sugar, and gives her one seventh of the sugar left in the sugar box. The two people get the same number of sugar. Guess how many pieces of sugar are there in Mr. Li's sugar box?
The equivalence relation of this problem

There were x pieces of candy in Teacher Li's candy box
Xiaoming's sugar number is: 1 + (x-1) (1 / 7)
2 + [X-1 - (x-1) (1 / 7) - 2] (1 / 7)
1+（x-1）（1/7）=2+【x-1-（x-1）（1/7）-2】（1/7）
So x = 36
Answer: there are 36 pieces of candy in Teacher Li's candy box

Solution equation: (15% x + 136) / x = 3:5

(15%x+136)/x=3:5
To get the denominator:
5(15%x+136)=3x
To get rid of the brackets:
0.75x+680=3x
transposition
680=3x－0.75x
merge
680＝2.25x
Divide both sides by 2.25
x＝2720/9
For reference! Jswyc

Fill in the following numbers: 5,2,10,4,15,6, (), ()

20.8

It is known that {an} is an arithmetic sequence. If A1 ＞ 0, A2009 + A2010 ＞ 0, A2009 · A2010 ＜ 0, then the maximum natural number n which makes the first n terms and Sn ＞ 0 hold is ()
A. 2010B. 2009C. 4019D. 4018

∵ the arithmetic sequence an with positive first term satisfies: A2010 + A2009 > 0, a2010a2009 < 0, ∵ A2009 > 0, and A2010 < 0, ∵ a1 + a4017 > 0, a1 + a4019 < 0. From Sn = n (a1 + an) 2, s4017 > 0, s4019 < 0

Finding the initial value of the equivalent differential equation of ∫ f (x, y) DX (in the range of x0-x)
The meaning of this question is not very clear

Let me give you an example, such as finding the differential equation corresponding to f (x) = ∫ [0 → x] TF (T) DT - ∫ [0 → x] XF (T) DT
This is an integral equation, which can be transformed into a differential equation
The original formula is: F (x) = ∫ [0 → x] TF (T) dt-x ∫ [0 → x] f (T) DT (1)
The derivation of X on both sides is: F '(x) = XF (x) -∫ [0 → x] f (T) DT XF (x)
That is: F '(x) = ∫ [0 → x] f (T) DT (2)
Further derivation: F '' (x) = f (x)
So we get a differential equation: F '' (x) = f (x)
Then, we substitute x = 0 into (1) (2) to get f (0) = 0, f '(0) = 0
These are two initial conditions, so that the original integral equation is transformed into an equivalent initial value problem of differential equation
f ''(x)=f(x)
f(0)=0
f '(0)=0
I don't know if I have solved your problem. If you have any questions, please ask me

1 () () 7 15 find the rule and fill in the numbers in brackets?
Such as the title
1 () () 7 15 find the rule and fill in the numbers in brackets?

1 1 3 7 15
The largest odd number of n power less than or equal to 2

A is a natural number greater than 0. When a 2 () is a false fraction, when a = (), it is equal to 3

Take a / 2 as an example
It is a false fraction when a = 2
When a = 6, it is equal to 3

What are the English words of rational number, real number, natural number and integer? What is a single letter?
For example, does n mean nature?
Please answer clearly

Rational number Q
Real number r
Natural number n
Integer number I