A 400 word letter to a distant child

A letter to Western children: Hello! My name is Liu Kelu. I'm a student of class 5 (2) of Qilin Primary School of Nanshan experimental school. I'm very cheerful. I like swimming, reading and listening to music. I'm very honored to organize "hand in hand" activities with your school. I hope we can become good friends

Composition: a letter to a distant child
(400 words)

A letter to a friend from afar
Dear friends of the same age
My name is * *, 11 years old, studying in Xi'an * * primary school. I'm a cheerful and sunny girl, like playing the electronic organ, playing table tennis, swimming, painting I have many friends around me, but I hope to be friends with you far away
I see from the TV that you are still reading in the shabby classroom, writing on the shabby desks. There is no fan in summer, no heating in winter I just know how happy I am
I feel deeply when I see your learning conditions. I bought some learning tools for you with my pocket money. There are thick dictionaries, pencils, pens and inks for writing, and some mathematical calculus books and manuscript papers for learning. When I think that these things will be delivered to you soon, your bright smile will appear in front of my eyes, I hope you can enter the bright classroom as soon as possible, use brand-new desks and chairs, carry beautiful schoolbags, and study in a good environment
A new year, a new beginning, a new hope, a new starting point. I hope you will get better grades in the new semester!
wish
Friends of the same age:***
February 25th

In the known space quadrilateral oabc, OA = OC, Ba = BC, points e, F, G and H are the midpoint of OA, AB, BC and co respectively. We prove that efgh is a rectangle
Why should the rectangle be 90 degrees? You can do that, too?

Because OA = OC, Ba = BC, points e, F, G and H are the midpoint of OA, AB, BC and C0 respectively
So EF is parallel and equal to 0.5bo
GH parallel and equal to 0.5bo
So EF is parallel and equal to GH
Similarly, FG is parallel and equal to eh
So efgh is a rectangle
Ability is limited, can't use mathematical symbol to express completely, please make do with

There are 840 tons of goods to be transported by two transport teams. Team a has 12 cars with a load of 5 tons, and team B has 15 cars with a load of 3 tons. According to the transport capacity of the two teams, how many tons of goods should each team carry?

(12 × 5): (15 × 3) = 4:3; team a: 840 × 44 + 3 = 480 (tons); Team B: 840 × 34 + 3 = 360 (tons); answer: team a should transport 480 tons, team B should transport 360 tons

First simplify and then evaluate: (a + B + C) 2 + (a + B-C) 2 - (a-b-c) 2 - (a-b + C) 2, where a = 54 and B = - 25

The original formula = (a + B + C) 2 - (a-b-c) 2 + (a + B-C) 2 - (a-b + C) 2 = (a + B + C + a-b-c) (a + B + C-A + B + C) + (a + B-C + A-B + C) (a + b-c-a + B-C) = 2A (2B + 2C) + 2A (2b-2c) = 2A (2B + 2C + 2b-2c) = 8ab, when a = 54, B = - 25, the original formula = - 250

The speed of train is 60% faster than that of car. How much slower is the speed of car than that of train?

6 = 37.5% a: the speed of a car is 37.5% slower than that of a train

In triangle ABC, BC = 6, AB + AC = 10, then the maximum area of triangle ABC is

If the three sides are 6 6 4, the area is 8 times root 2. If the three sides are 5 5 6, the area is 12, so

It takes 3 hours for a car to go up the mountain, with a speed of 30 km / h, and 2 hours for a car to go down the mountain. What is the average uphill / downhill speed of this car?

3 × 30 = 90 (km)
90 × 2 ÷ (3 + 2) = 36 (km / h)

Given that at least one of the functions y = x · x + 4ax-4a + 3, y = x · x + (A-1) x + a · a, y = x · x + 2ax-2a has zero point, find the range of real number a

The thought of using the method of proof to the contrary
Let y = x · x + 4ax-4a + 3, y = x · x + (A-1) x + a · a, y = x · x + 2ax-2a have no zeros,
Then Δ = (4a) ^ 2-4 (- 4A + 3) < 0
Δ=（a-1）^2-4a^2＜0
Δ=（2a）^2-4(-2a）＜0
3 / 2 ＜ a ＜ 1 / 2
A ＞ 1 / 3 or a ＜ - 1
-2＜a＜0
So the range of a is - 3 / 2 ＜ a ＜ - 1
Therefore, we have the idea of proof to the contrary when at least one of the functions y = x · x + 4ax-4a + 3, y = x · x + (A-1) x + a · a, y = x · x + 2ax-2a has zero
A ≥ - 1 or a ≤ - 3 / 2 is obtained

The road between town a and town B is 180 kilometers long. Xiao Li has driven his car from town a to town B for 20 kilometers, using 2 liters of gasoline. According to this calculation, how many liters of gasoline will he need to complete the whole journey

A 400 word letter to a distant child