The fifth question on page 42 What does that rich man mean? What does Andersen mean when he answers the rich man's question? The content is as follows: Witty answer After becoming a famous writer, Antoine still wore an old hat as usual. One day, he was walking in the street. Walking along the crossroads, a carriage was beside him. He was a well-dressed man walking down from the carriage. The man looked at Andersen for a long time and said, "what's on your head? Is that a hat? " After listening to him, Andersen laughed. He looked at the man for a moment and said, "Sir, what's under your beautiful hat? Is that a brain? " The rich man's arrogance turned into embarrassment. Andersen had gone a long way, and he was still standing there, not knowing what to say.

Andersen's old hat is too shabby
Rich people have beautiful hats, but they are too poor

Answers to question 5 on page 4 of winter vacation homework of grade 5 mathematics in Beijing Normal University edition of new curriculum standard of Yanbian University Press
Xiao Hong, Xiao Ming and Xiao Yu go to the library regularly. Xiao Hong goes to the library every five days, Xiao Ming every seven days and Xiao Yu every eight days. If they go to the library today, how many days will it take them to go to the library at the same time next time?

Is the least common multiple of 5.7.8, 5 * 7 = 35 (days) 35 * 8 = 280 (days)
A: it will take 280 days

Given the square of a + 2A = 1, find the square of 3A + 6A + 2

a²+2a=1
3a²+6a+2
=3（a²+2a）+2
=3+2
=5

If we know P (T1 + 1,2t2) and translate it to p '(0,0) according to vector (1,2), then T1 = -, T2=——

P (T1 + 1,2t2), according to the vector (1,2) translation to p '(0,0)
Then p '(0,0) is translated to the point (- 1, - 2) by vector - (1,2) = (- 1, - 2)
That is, P (- 1, - 2),
And P (T1 + 1,2t2),
∴ t1+1=-1,2t2=-2
∴ t1=-1,t2=-1

What examples show that the effect of force is related to the three elements of force?

Push the door: push the door from the end of the door leaf (far away from the shaft), the closer it is to the shaft, the harder it is!
The direction of the force determines the direction of the effect

5 out of 6 x + 1 = 3 out of 7, please solve the equation

5x out of 6 + 1 = 3 out of 7
5x out of 6 = 3-1 out of 7
5x out of 6 = 10 out of 7
X = 10 out of 7 x 6 out of 5
X = 12 out of 7

If the addition and subtraction of fraction 4x \ = A / x + 2-B / X-2, then a & sup2; + B & sup2=
It is known that 4x (X & sup2; - 4) = a (x + 2) - B (X-2)

How to calculate covariance

The definition of E [(x-e (x)) (y-e (y))] is called the covariance of random variables X and y, which is recorded as cov (x, y), that is cov (x, y) = E [(x-e (x)) (y-e (y))]
Note that E [(x-e (x)) (y-e (y))] = e (XY) - E (x) e (y)

(- 0.75) + (+ 0.125) + (2 and 3 / 4) + (18 and 3 / 7) + (- 6 and 1 / 8) - (- 10 and 4 / 7)
2 / 3-7 / 8 - (1 and 1 / 3) + (2 and 1 / 8) + | - 2|

1. (- 0.75 + 2 and 3 / 4) + (0.125-6 and 1 / 8) + (18 and 3 / 7 + 10 and 4 / 7) = 2-6 + 19 = 15
2. (2 / 3-1 and 1 / 3) + (2 and 1 / 8-7 / 8) + 2 = - 2 / 3 + 1 + 2 = 2 and 1 / 3
Note: 3 / 4 = 0.75, 1 / 8 = 0.125,

How to prove LIM (1 / N & # 178; + 1 / (n + 1) & # 178; +... + 1 / (2n) & # 178;) = 0 N →∞ with pinch theorem

Let Sn = 1 / N ^ 2 + 1 / (n + 1) ^ 2 + +1/(n+n)^2
Then,
1/n^2