My daughter does one math problem and can t do it

LS is so complicated that elementary school children can't understand it.

The number of people in a row of triangles is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12....

There are 45 people in platoon 9, 55 people in platoon 10, 66 people in platoon 11, 78 people in platoon 12, and the number of other platoons does not meet the requirements of 40 80;

If you become a square queue, there are 2 more people: in the above 4 types, you can find that only 11 rows are satisfied, with a total of 66 people;

So there are 66 people in this class, which can be arranged in 11 rows, and there are 8 rows and 8 columns in a square, and there are 2 more people.

Solution: It is known that the number of people in this class is between 40 and 80 = "can only be 7 * 7 + 2 = 51 or 8 * 8 + 2 = 66

Can be arranged in a regular triangle, so that the regular triangle queue can only be:

First Row 1 Second Row 2 Third Row 3

The sum is (1+n)*n2 (set to n rows).

Let the total number of people be 51 = (1+n)*n 2 Since n has no integer solution, the total number of people cannot be 51

Only when the total number of students is 66, 66=(1+n)*n 2 can be obtained by n=11, so the total number of students in this class is 66.

I wish your daughter progress in her studies!!

44 people, 13 people in each column; 56 people, 18 people in each column; 65 people, 21 people in each column; 74 people, 24 people in each column.

The three numbers a, b, c, suppose a is the largest, c is the smallest, and b is the middle, then the difference must be abc-cba where b in the middle is invariant (e.g., 851-158,,,279-972) and thus the answer is obtained.

And because a > c, when two numbers are subtracted, b must become 9 (e.g., 851-158=693).

Then look at the first bit, the first bit must be the largest number a - the smallest number c, in the process of subtraction, as I just said, the middle bit becomes 9, to borrow the upper digit, so the first bit in the result should be.

a-c-1, and then look at the last digit, it must be borrowed, and the result is 10-a+c

Suppose x=a-c-1

Putting these three numbers together is x9 (9-x).

If you rearrange it again, 9 will definitely be the first.

x and (9-x) which is larger and which is in the middle.

If x is greater than 9-x, i.e., x>9-x, i.e., x>, i.e., 5,6,7,8,9

Then the order should be 9x (9-x).

If you do it again, the result should be that the middle bit is still 9

The first digit is 9-(9-x)-1=x-1

The last digit is 10-9+9-x=9-x+1

It can be seen that if x > or above), the first digit becomes x-1, which is 1 less than the original, and the last digit increases by 1, becoming 9-x+1, until it becomes below 5, which is 4

If x is smaller than 9-x, i.e., x<9-x, i.e., x<, i.e., 0,1,2,3,4

Then the order should be 9 (9-x)x

At this time, 9-x is the middle bit, and 9-x is >, and after the operation, the same first digit decreases, and the last digit increases, until below 5, which is 4

The result is 495, the middle position is still 5 after the rearrangement, 5-1 becomes 4, 4+1 becomes 5, and so on and so on and so on it is always 495

It can be concluded that any three numbers, after a sequence from largest to smallest and one from smallest to largest, are subtracted, and the first and last digits are added to give 9, and the middle digit is 9, as proved above (the first digit is a-c-1, and the last digit is 10-a+c).

When the difference between the first digit and the last digit is 1, after many operations, the two numbers increase and decrease one by one, and finally become 4 and 5

All the last results are 495

That's what my daughter said in his textbook, Can you tell me the answer, and then tell me why, and I'm like telling my daughter why, thank you, because I didn't study well when I was a child, and now I regret it.

Little Red Belt's money is poor.

yuan, and the sum of the two du's money zhi just happened to buy this book, saying that dao ming xiaohua brought one yuan.

Dedicated to the four corners. Just use one yuan hexagonal genus plus one yuan four corners = the price of this ***, the number of money that Xiaohong brought = the price of this *** - one yuan four corners, the money brought by Xiaohua = the price of this *** - one yuan hexagon. The first-grade math homework problems are getting more and more difficult, and 1+1 can be done as homework in the past.

Xiaohong is 1 yuan and 4 jiao, and if you can buy it with Xiaohua, it means that Xiaohua brought 1 yuan and 4 jiao.

The same is true for the little red belt is 1 yuan and 6 jiao, and the ** of the book adds up to 3 yuan.

Let me tell you、、This question is actually quite simple:

yuan) (this is the price of the book).

yuan) (this is Xiaohong's money).

yuan) (this is Xiaohua's money).

Absolutely、、With my IQ.。

The price of the book

Money: yuan) zhi

Xiaohong: Yuan) Xiaohua: Yuan).

The sum of the dao with the difference in money is the price of the book.

yuan) (this is the price of the book).

yuan) (this is Xiaohong's money).

yuan) (this is Xiaohua's money).

Answer: The book costs 3 yuan, Xiaohong brought yuan, Xiaohua brought yuan.

The total amount of money between the two of them to buy a ***, then the amount of money that Xiaohong has is the money brought by Xiaohua. So Xiaohua brings one yuan and four corners; In the same way, the money of the little red belt is one yuan and six jiao, and the price of the book is yuan.

This book = meta.

Little red = yuan. Xiaohua = Yuan.

Yuan A: The book costs 3 yuan.

Xiaohong brought the yuan.

Xiaohua brought Yuan.

Isn't it just 3 yuan a book? Xiaohong brought Yuan, and Xiaohua brought Yuan. Don't overcomplicate the issue.

Answer: This book costs three yuan, Xiaohong brought one yuan and six corners, and Xiaohua brought one yuan and four corners.

Set Xiaohong with money x, Xiaohua with y, the ** of the book is z, according to the title:

x+，y+,x+y =z.

Solving the system of equations yields x= , y=, z=3 units are yuan.

One dollar and four corners plus one dollar and six corners equals the amount of money needed for the book. Subtracting the amount of money they needed for the book leads to the second problem.

Xiaohong brought one yuan and six corners, Xiaohua brought one yuan and four corners, and this book costs 3 yuan.

Solution: Set the small red belt x yuan, and the small Chinese belt y yuan.

The system of equations that can be listed is.

Inner x+y=x+

x+y=y+

x=? y=?

Do the math yourself.

Thinking like this, they each bought a copy, and the money for the two of them was just one yuan. The money on them is just enough to buy one book, and the poor money is just enough to buy another, which means that a book is 3 yuan.

Solution: Set Xiaohong with x yuan, Xiaohua with Y yuan, this book needs z yuan.

According to the title, x+y=z, x=, y=

Solution, x=, y=, z=3

Answer: This book costs 3 yuan, Xiaohong brought yuan, Xiaohua brought yuan.

yuan) (this is the price of the book).

yuan) (this is Xiaohong's money).

yuan) (this is Xiaohua's money).

The money of the little red belt: 30-14 = 16 jiao Xiaohua 30-16 = 14 jiao.

One yuan four corners = 14 jiao One yuan six corners = 16 jiao Buy this book: 14 + 16 = 30 jiao = 3 yuan.

This book = meta.

Xiaohong brought the yuan.

Xiaohua brought Yuan.

Got it?

One yuan four corners + one yuan hexagons = three yuan divided by two = yuan.

This is essentially piecing together a numerator with a denominator and then adding the rest.

Take a simple example such as x 2 (x-1).

How does Molecule X 2 change? The molecule contains a target (x-1) along this line of thought x 2= (x-1)*(x+a)+b=x 2-a+(a-1)x+b

It is obtained that a-1=0 b-a=0 Therefore, a=1 b=1, taking question (1) as an example, (2x, 2+3x+6) (x-1), the molecule should contain the target x-1

Thus 2x 2+3x+6=b*(x-1)(x+a)+c=bx 2+b(a-1)x-ab+c

b=2 b(a-1)=3 c-ab=6, and finally a=5 2 b=2 c=11

2x^2+3x+6)/(x-1)=[2*(x-1)(x+5/2)+11]/(x-1)=2x+5+11/(x-1)

In the same way, the result of problem 2 is 5x 2-1-1 (x 2+2).

You have to read more and do more questions.

Nothing will be made up.

Listen carefully to the class.

An important point, you can't copy homework, thank you.

Summing up, the middle can be eliminated, leaving only 1 2-1 2010

1.Let 2x=x squared -x

It is derived that x= because the elements in the set cannot be repeated.

Therefore, the value range is {x|x is not equal to 3, x is not equal to 0, x belongs to the set of real numbers}2 solves two systems of equations.

x=3, y=-7

So the enumeration method {x=3,y=-7}

Descriptive {x,y|｛3x+y=2 , 2x-3y=27｝3。｛x|x=3n+1, n belongs to the set of positive integers}

Belch.. Please automatically convert to symbolic representation.

The computer will not play.

1.Let y be the real number of the conjunction, then y>2x is the intersection of y< x 2-x.

If you make two function images, you can see that the area where the two images intersect is their set

2.Equivalent to solving equations, 3

1 There are no two identical terms in the set, so 2x is not equal to x, 2-x x is not equal to 0, and x is not equal to 3

2 y=2-3x y=2 3x-9 2-3x=2 3x-9 x=3 y=-7 So the example is, the description is.