Ask the master to help solve a line test problem, and you want to solve the process specifically, th

Hua Luogeng Gold Cup.

This is a question in the finals.

Solution] From the title, it is already known that there are 50 boys and girls attending the party. Therefore, if the difference between the number of boys and the number of girls is known, then it is enough to know how many boys are among the 50 students.

In order to make the conditions in the question easier to analyze, we might as well reverse the order of the girls and look back to the front. That is: the last girl to attend shook hands with 7 boys; The penultimate girl shook hands with eight boys; The third-to-last girl shook hands with nine boys; And so on, the first girl to be present (i.e., the last to last) shook hands with all the boys, and it was immediately clear that there were six more boys than girls, and by a simple calculation we obtained:

The number of boys is 28.

A: Of the 50 students, 28 are boys.

Method 2: Suppose there are n women, then there are 50-n men. For the number of handshakes between the last female and the male, there is an equation: 7 = (50-n) - (n-1), so n = 22, male 28.

Answer: AAnswer: Let the number of boys be x and the number of girls be y.

x+y=50

Because the first girl shakes hands with x boys, and the second girl shakes hands with x 1 boys. The last girl, the y-th girl, shook hands with the 7 boys.

You can get: 1+x y+7

Solution: x+y=50

1+x＝y+7

x=28 y=22

If there are x boys, then there are 50-x girls.

According to the last girl and 7 boys, it can be seen that there are 7-1 = 6 more boys than girls.

Column equation: x-(50-x)=6

Solution: x=28

One. 45-33=12, from the equation two to proportional, so 12:30=48:32+x, the solution is x=88

First of all, we must know the binomial theorem.

a+b)^n＝c(n,0)*a^n+c(n,1)*a^n-1*b^1+…+c(n,r)*a^(n-r)*b^r+…+c(n,n)*b^n(n∈n*)

coefficient sum = 2 n

Therefore, [11x 5 +(1 x) (1 2)] 5 can be deformed into a standard binomial [( 11x 5) 2+x (-1 2)] 5, and the general term is c(5,r)*(11x 5) (10-2r)*x (-r 2).

Therefore, when 10-2r-r 2=0, that is, r=4, the constant term is obtained, and r=4 is substituted into it, and the constant term c(5,4)*(11x 5) 2=11 is obtained

According to the meaning of the question 2 n=11, it is obviously impossible to solve it.

The landlord may have typed the wrong number, such as [16x 5 +(1 x) ]5 so that there is 2 n = 16

Solve n=4 and (a 2+1) 4=a 8+4a 6+6a 4+4a 2+1 and obviously 6a 4=54

The solution is a = 3

Solution: This requires the knowledge of Yang Hui's triangle, Yang Hui's triangle:

In the nth-1st binomial of each row with the table, the coefficients of each formula, such as the fifth, are .

i.e.: (a+b) 5=a 5+5a 4b+10a 3b 2+10a 2b 3+5ab 4+b 5

The constant term of 11x 5 +(1 x) ]5 is:

5*11x 5*[1 x)]4 = 11, so the sum of the coefficients is 11

But there is no binomial formula in which the sum of the coefficients is 11...

You can analyze it first.

I don't know how big a piece of land is, but I know what the proportion of celery, cucumber, rape, and leeks is, and I also know that the area of leeks is 160 square meters, accounting for 32%1) to know the total area of the land.

160 500 (m²) (the total area of this vegetable plot) 2The proportion of celery is 28%, then the area of celery is 500 * square meters), the proportion of cucumber is 25%, the area is 500 * square meters), the proportion of rape is 15%, then the area is 500 * square meters) 3From the above, the area of cucumbers is 125 square meters, and the number of cucumbers collected per square meter is 15kg, and the total number of cucumbers can be obtained.

There are no kilograms to buy dollars, and you can calculate how much money you can buy in total.

1875*).

1.160 square meters is 32%, total area = 160 square meters.

A is definitely related to C and c is directly in the variance formula for individual assets, and d covariance is the value needed to calculate the correlation coefficient. Only b has nothing to do with it.

(1) When the manufacturer's profit is the largest, there is w=vmp=p·mp, that is, the solution is: l=60.

The denominator is the same, the numerators are added, and their sum is:

2012+1) (2012 2) = 2013 1006 The denominator is 2013, which is just the same as the 2013 of the numerator, and the result is 1006

The answer is 1006