Math problems, to the process, everyone helps

It was observed that the number in row n of column 1 was n 2

The number in row nth of column 2 was observed to be 4n

The number in row nth of column 3 was observed to be 5n

The number in row n of column 4 was observed to be 8+2n

1) What is the number in column 2 of row 10?

4*n=4*10=40

2) What are the rows and columns where the number 81 is located?

81 is an odd number, and the numbers in the first column are all odd numbers, so it is only possible to substitute in the first column.

Get 81=9 2 so 81 in column 1 in row 9.

3) What are the rows and columns where the number 100 is located?

100 = 10 2, so 100 is in column 1 in row 10.

Let the number of rows be x, and the first column is x;

The second column is 4x; The answer to the first question is 40;

The third column is 5x;

The fourth column is 2 (x+4);

The answer to the second question is: the first column of the ninth row;

The answer to the third question is: the first column of the tenth row and the second column of the 25th and the third and fourth columns of the 46th of the 20th row. Oh.

The first column is N2

The second column is 4n

The third column is 5n

The fourth column is 10+2 (n-1).

So the number in column 2 of row 10 is 4*10=40

So the number 81 is in the first column of row 9.

So the row and column where 100 is located are the first column in row 10; Row 20, third column, row 46, fourth column.

1.A:

x 100, fee =

x 100, fee =

B x 60, fee =

x 60, fee =

2.When x=200, then.

A: Fee = B: Fee =

3.If this is a continuation of the 2 questions above, then answer A.

If not, it is a separate question, then it is necessary to assume that A is cheaper or B is cheaper and the same three cases are calculated.

(1) If you buy x items in store A, there are two situations: one is when x is greater than 100 pieces, the yuan payable;

Second, when x is less than or equal to 100 pieces, the yuan payable.

In the same way, there are two situations when buying x items in store B: one is that when x is greater than 60 pieces, 2 (x-60) + yuan should be payable;

The second is when x is less than or equal to 60 pieces, the yuan payable.

2) purchase 200 pieces to choose the first case calculation; That is, store A should pay 2 (x-60)+ for store B

430 yuan. 3) 420 430 Therefore, it is cost-effective to go to store A to buy.

Adopt if helpful. If you don't understand, you can ask.

(1) Home A: When 0 x 100, y=

When x 100, y=

B: When 0 x 60, y=

When x 60, y = 150 + 2 (x-60).

2) Home A: y=, when x=200 Home: y=150+2 (x-60), when x=200.

y=yuan) y=150+280=430 (yuan).

3) When y is equal, then.

Go to the brackets. The coefficient of the shift is reduced to 1 to obtain x=300

So when x=300, it's the same for both families.

When x 300, B is cost-effective.

When x 300, A is cost-effective.

I can't help with the first question.

2) 200 * yuan), 60 * yuan, (200-60) * 2 = 280 yuan, 280 + 150 = 430 yuan.

3) Go to the first factory.

(1) When x 100: When x > 100:

When B x 60: When x > 60 2 (x-60) (2) Factory A 200 * Yuan), Factory B 60 * Yuan, (200-60) * 2 = 280 Yuan, 280 + 150 = 430 Yuan.

3) A factory is cost-effective.

The straight line y=kx+b is parallel to the straight line y=-2x+4

So. k=-1

The intersection of the line y=3x+6 on the y-axis is (0,6) so. The intersection of y=-x+b on the y-axis is the analytic expression y=-x+6 of the straight line (0,6)b=6

1. Square side length: 1 4=

2. Isosceles triangle side length:

3. The area of the four isosceles triangles (the area of the green area) is :(

Isosceles triangle side length:

Square side length: 1 4=

The area of the four isosceles triangles (the area of the green area) :(

Let 2x 2+3x+5m=f(x).

f(1)＞0

Then you can solve it, and it should be fine, hehe.

Answer: 7.

Process: Ask what to set up what, assume x people.

After one round: x number of people were infected, plus the number of people who were already sick, a total of 1+x people were sick.

After two rounds: ......Analyze it yourself.

The final formula: (1+x)(1+x)=64

x^2=64 x=8

It means that one person infects eight people at a time.

Solution: 1, bring the coordinates of point e into the linear equation to obtain: 0=-8k+6, you can get k=, and the linear equation is: y=

2. The bottom of the triangle Pao is OA, and the height is the ordinate of the P point, and the P point is brought into the linear equation to obtain: Y =, the area of the triangle Pao is s=6*y 2=6 (. Since point p moves in a straight line within the second quadrant, so -83, when the area of the triangle opa is 27/8, i.e. s=27 8=, so x=, and the value of x is brought into the equation of the straight line to get y=, so in this case, the coordinates of point p are (,1,125).

It's been many years since I left middle school, and I don't know the rules for doing questions anymore. Just read it, and then sort it out yourself.