English translation Boffins are the clever ones in class .They always come out top in tests.To be a boffin ,you must be good at all the subjects . Boffins are clever ,but are never the most popular people in the school .They have freiends amongst themselves.But In society, they are normally shy and outlying. Boffins prefer their studies to the company of other people.Edwin is the oclassic example of a boffin.He has friends, but they are also boffins.Edwin is extremely clever.His vosice has a very strong British accent that other people find funny . A boffin’ s interest is something that other people may not be interested in.For example ,they may like to play games on computer that others may find boring .In their spare time,boy boffins feel like playing war games and strategies .Boffins prefer technology such as computers to having sports outside.Normally , they are not very sporty and arebad at P.E. Boffins also act in a manner that is slightly strange.They don’t care what other people will thihk of them because of these outbursts . While most children take the word “boffin”in a negative way,adults,especially teachers approve of boffins.Boffins spend their time in class actually listening attentively instead of messing around .This is mainly the reason why they appear to be more intelligent than everyone else around them. Although they may not be the most exciting people,I like boffins .They have intelligent minds of their own and are not afraid to show them.Boffins are the cleverest ones ,and there’s nothing bad about standing out in that way.

"Boffins" (researchers or technologists) are often very smart in class. They are always at the top of the class examination. To be a "boffin", you must be good at all subjects. Boffins are very smart, but they are not the most popular people in school. They just make friends with each other in "boffins"

English translation
lt was long holiday .we left beijing on february 1st and got to harbin on the 2 nd.on the first day,i went to a park with my parents.on the 3rd,i went skiing .on the 4th ,i did my
homework.on the 5th ,i went ice- skating.on the 6th,i bought presents for my friends.we got back to beijing by piane on the 7 th.for the last day of the holiday,we relaxed and prepared to go back to work or school.

It was a long holiday. We left Beijing on February 1st and arrived in Harbin the next day
On February 3, we went skiing. On February 4, I finished my homework
On the 5th, I went skating. On the 6th, I bought some presents for my friends. On the 7th, we flew back to Beijing
For the rest of the holiday, we relax and get ready to work

In the sequence {an}, A1 = 1, when n ≥ 2, a1a2a3 ··· an = n & # 178;, compare the size of an, a (n + 1) and explain the reason

a1*a2*a3*…… *an= n²
a1*a2*a3*…… *a(n-1)= (n-1)²
By dividing the first formula by the second formula, an = n & # 178; / (n-1) &# 178;, an > 0
Similarly: a (n + 1) = (n + 1) & # 178 / N & # 178;
Then: a (n + 1) / an = [(n + 1) &# 178;] / [n & # 178; / (n-1) &# 178;]
= (n+1)²(n-1)²/ (n²)²
= [(n²-1)/n²]²
= (1- 1/n²)² a(n+1)

If the mass of a rectangular aluminum block with a length of 10cm, a width of 5cm and a height of 8cm is 1080g, what is the density of the aluminum block kg / M;?

Length into rice
The volume is 0.1 × 0.05 × 0.08 = 0.0004 cubic meters
1080g = 1.08kg
The density is 1.08 △ 0.0004 = 2700kg / M and 179;

What is the first level operation, what is the second level operation and what is the third level operation

Addition and subtraction are first order
Multiplication and division are two levels
The square root is three levels

When Xiaoming uses a voltmeter with two ranges of 0-3v and 0-15v to measure a dry battery, the indication of the recorded voltmeter is 7.5V, which is obviously wrong. The reason for the error is that_____ . the actual voltage may be

Connect to 0-3v range and read according to 0-15v range
The actual voltage may be 1.5V

(1 + 40%) * 80% - x = 24

(1+40%)*80%-x=24 1.4×0.8-x=24 1.12-x=24 x=1.12-24 x=-22.88 (1+40%)*80%-x=24

Four practical questions
1. The store shipped 6 tons of apples, 2 / 3 more than the pears. How many tons of pears?
2. The store transported 6 tons of apples, 2 / 3 more than the weight of pears, and how many tons more than pears
3. The weight of pears and apples from the store is 6 tons. The weight of pears is 2 / 3 of that of apples. How many tons does the apple weigh?
4. The pear transported by the store is 6 tons less than that of the apple, and the weight of the apple is 2 / 3 more than that of the pear. How many tons of the pear are transported?
2 / 3 = two thirds

1. 6 ÷ (1 + 2 / 3) = 6 × 3 / 5 = 18 / 5 (ton)
2. 6 ÷ (1 + 2 / 3) × 2 / 3 = 6 × 3 / 5 × 2 / 3 = 12 / 5 (ton)
3. 6 ÷ (1 + 2 / 3) = 6 × 3 / 5 = 18 / 5 (ton)
4. 6 △ 2 / 3 = 9 (ton)
All right

Given the hyperbola 2x ^ 2-y ^ 2 = 2, the length of its chord PQ is twice the length of its real axis. If the line L where the chord PQ lies passes through point a (root 3,0), the equation of line L is obtained

2x^2-y^2=2
x^2-y^2/2=1
A = 1, real axis length = 2A = 2
Let l equation: y = K (x - √ 3)
Generation 2x ^ 2-y ^ 2 = 2
2x^2-k^2(x-√3)^2=2
(2-k^2)x^2+2√3k^2x-(3k^2+2)=0
x1+x2=2√3k^2/(k^2-2),x1x2=(3k^2+2)/(k^2-2)
(x1-x2)^2=(x1+x2)^2-4x1x2=16(k^2+1)/(k^2-2)^2
Length of chord PQ = √ [(1 + K ^ 2) * (x1-x2) ^ 2] = 4 (k ^ 2 + 1) / | K ^ 2-2 | = 2
So, | K ^ 2-2 | = 2 (k ^ 2 + 1)
So, 2-k ^ 2 = 2K ^ 2 + 2
3k^2=4
k=±2√3/3
L equation: y = ± 2 √ 3 (x - √ 3) / 3

How many amperes is a 4 square line current

Calculation of conductor cross section and current carrying capacity
1、 The safe current carrying capacity of general copper conductor is determined according to the maximum allowable core temperature, cooling conditions and laying conditions. The safe current carrying capacity of general copper conductor is 5 ~ 8A / mm2, and that of aluminum conductor is 3 ~ 5A / mm2. The safe current carrying capacity of general copper conductor is 5 ~ 8A / mm2, The safe current carrying capacity of aluminum conductor is 3 ~ 5A / mm2. For example, the recommended safe current carrying capacity of 2.5 mm2 BVV copper conductor is 2.5 × 8A / mm2 = 20a, and the recommended safe current carrying capacity of 4 mm2 BVV copper conductor is 4 × 8A / mm2 = 32A
2、 Calculate the cross-sectional area of copper conductor. Using the recommended value of safe ampacity of copper conductor 5 ~ 8A / mm2, calculate the upper and lower range of cross-sectional area s of selected copper conductor: S = < I / (5 ~ 8) > = 0.125 I ~ 0.2 I (mm2) s --- cross-sectional area of copper conductor (mm2) I --- load current (a)
3、 Generally, there are two kinds of load for power calculation, one is resistive load and the other is inductive load. For resistive load, the formula is p = UI. For fluorescent load, the formula is p = uicos ф, in which the power factor of fluorescent load is cos ф = 0.5, When unified calculation of household appliances, the power factor cos ф can be taken as 0.8. That is to say, if the total power of all household appliances is 6000 watts, the maximum current is I = P / uCOS ф = 6000 / 220 * 0.8 = 34 (a). However, in general, household appliances cannot be used at the same time, so a common factor is added, and the common factor is generally 0.5, The above calculation should be rewritten as I = P * common coefficient / uCOS ф = 6000 * 0.5 / 220 * 0.8 = 17 (a), that is to say, the total current value of this family is 17a. The air switch of the main brake can not use 16a, but should use a current greater than 17a