The sooner you solve this number series problem, the better, and the more points you can solve!!

There is a problem with your translation. The meaning of this question is:

Let u 1, u 2,are independent random variables that are uniformly distributed over unit intervals [0, 1]. When 0x is the smallest integer nSeek the expectation of n x.

Answer: For this question, it is possible to consider doing it positively.

It will cause us unnecessary trouble, so we should think about the problem in a different way. Mathematical ideas are broad and profound. If this road is not passable, the key will collapse, and Xiang will go another way.

Therefore, when we do this kind of question, we should deal with it according to his opposing problem.

Step 1: Find a situation where there is no pair, let's set this as event p

Here's an analysis of how to answer this event.

In the chapter on probability, we know that finding a probability requires the total basic event, and the total event under that condition. It has 10 pairs of shoes, 20 and only 8 of them.

For this question, the total basic event is [c20

8] Shecong 20

Only 8 of them are selected, and I will put a comma between these two numbers below. Please forgive me for not being able to play out due to the bad clothes), and so on.

Choose one of the ten pairs of shoes [C10,1], and then choose any one of these shoes to come out as [C2,1].

Then choose one of the remaining 9 pairs of shoes as [C9,1], and then choose any one of these shoes as [C2,1].

Then choose any pair of the remaining 8 pairs of shoes as [C8,1]. Then choose any one of these shoes as [C2,1].

And so on until you choose one of the remaining 3 pairs of shoes [C3,1], and then choose any of these shoes as [C2,1].

then there is p= [c20,8].

So the probability of at least one pair is p(find)=1-p

There are questions in the question"At least"Two words.

Obviously, the reverse side is used here.

The probability of not having a pair is (8 pairs of brothers are selected.)

Choose one of each).

p=(10*9/2*2^8)/(20!/(12!*8!The answer to this question is (1-p).

Solution: (1) From the title s3=6, a7=7:

3a1+3d=6,a1+6d=7

Solution: a1=1, d=1

So the general formula for the series an=a1+(n-1)d=n2) if bn=an*2 n-1, then bn=n*2 (n-1) so: tn=1*2 0+2*2 1+3*2 2+.n-1)*2^(n-2)+n*2^(n-1) （1）

Then: 2tn=1*2 1+2*2 2+3*2 3+.n-1)*2^(n-1)+n*2^(n) （2）

2) (1) De:

tn=－[2^1+2^2+2^3+..2^(n-1)]+n*2^(n)-1

2-2^n+ n*2^(n)-1

n-1)*2^(n)+1

3)cn???

1) a1 + a3 = 4 to get a2 = 2. There is a7 = 7 again. d=1, a1=2) dislocation subtraction.

tn=1*2+2*4+3*8+..n*2^n-n2tn=1*4+2*8+3*16+..n*2 (n+1)-2n is subtracted.

-tn=2+4+8+16+.2^n-n*2^(n+1)+n

tn=2^(n+1)-2-n*2^(n+1)+ntn=(1-n)2^(n+1)+n-2

tn=(n-1)2^(n+1)-n+2

3) What about CN??

1）an=n

2)tn=(1-n)2^(n+1）-2-n

3) Mathematical induction, 2 n=c1 n+.cn/n

The second question is the first floor, and everything else is wrong. The third question is wrong, and the 4th floor is correct.

Solution: Because the pin slag is vertical 8a2+a5=8a1q+a1q 4=0, that is, there are 8+q 3=0 , q=-2 , s5 s2=

a1(1+q+q 2+q 3+q 4) a1(1+q 2)=(1+q+q 2+q 3+q 4) (1+q 2)= 11 Deficit 5