Ask three math questions in a hurry!! Three math problems, help!!

1: odd function So f(-x)=-f(x) f(-1)=-f(1)=-1 2

f(1)=f(-1+2)=f(-1)+f(2) So f(2)=1

f(3)=f(1+2)=f(1)+f(2)=3/2 f(5)=f(2+3)=f(2)+f(3)=5/2

2: Even function so f(-x)=f(x) f(3)=f(-3)=0

f(x) is increasing at (0,+, so f(x) is less than 0 on (0,3) and f(x) > 0 when x is greater than 3

f(x) is an even function So, the image is symmetrical with respect to the y-axis, so f(x)>0 -3 at x<-3 so the solution of f(x) x<0 is (-3), (0,3).

3: odd function So f(-x) = -f(x) and f(0) = 0

f(6)=f(4+2)=-f(4)=-f(2+2)=f(2)=-f(0)=0

1. Because f(x) is an odd function on r, and f(1)=1 2, f(-1)= -1 2

So f(1)=f(-1+2)=f(-1)+f(2), so f(2)+f(-1)=1 2, so f(2)=1.

So f(5)=f(3)+f(2)=f(1)+2f(2)=1 2+2*1=5 2

There is a problem with the second question, please update the question.

3. From the meaning of the question: f(x+4)=-f(x+2)=f(x), so f(x+4)=f(x), and because f(x) is defined as an odd function on r, then f(0)=0, so f(2)=-f(0)=0, so f(6)=f(2+4)=f(2)=0

1，f(3)=f（1+2）=f(1)+f(2) ,f(5)=f(3+2)=f(3)+f（2）

So f(5) = f(1) + 2f(2).

Because it is an odd function, so f(-1)=-f(1), so f(-1)=-1 2

and f(-1+2)=f(1)=f(-1)+f(2), so 1 2=-1 2+f(2), so f(2)=1

Finally, the above equation is substituted f(5)=1 2+2*1=5 2

2,, Is there a mistake in the second question? It should be an increase or decrease function from 0 to positive infinity.

3, is an odd function, then there is f(-x)=-f(x), and because f(x+2)=-f(x), so f(x+2)=f(-x).

Since f(0)=0, f(-2)=f(2)=0, f(-4)=f(4)=0, f(-6)=f(6)=0

1.Assuming that the 100 digits of the actual number are a, the 10 digits are b, and the single digit is c, so 100*a+10*b+c=100*b+10*a+c+180 (the total number of students provided by the enumerator is 180 fewer than the actual total number), and a-b=2And because there are 36 people in each class, the three-digit number is a multiple of 36, and the hundred digits are 2 greater than the ten digits (at least starting from 2), so the total number of people is 648, 18 classes or 756, 21 classes or 864, 24 classes or 972 people, and 27 classes.

It is not an integer multiple, nor is it an integer multiple, so the Zhang family is more than 10 degrees, and the Li family is not more than 10 degrees. And the degree of the Li family must be even (otherwise the second decimal place is 5). , for multiples of which it is conformed to; , not satisfied; , not satisfied;

So Li's household electricity is 8 degrees, Zhang's is 13 degrees, Li Jiayuan, Zhang Jiayuan.

3.s=pi*r*r= where d is the diameter, and the large must be 20% larger than the small diameter, that is, the multiplier, so the area is multiplied by equals the times, so the large (square centimeters.

1 756 864 972 are all satisfied, is not missing the condition 2, set the electricity of each m n degree, the yuan is not or a multiple.

It can be seen that the electricity consumption of two companies cannot be lower than 10 degrees or higher than 10 degrees at the same time, so m>10 n<10

Zhang's fee is 10*

Away from home fee m*

10*16m-9m=136

m=13 n=8 if the condition is satisfied

3. The diameter of the large disc is 20% larger than that of the small disc

The diameter of a large disc is 6:5 than that of a small disc

The area of a large disc is 36:25 compared to that of a small disc

The area of the small disc is 50 square centimeters.

The area of the large disc is 72 square centimeters.

The large disc is 22 square centimeters larger than the small disc.

The number of students in this school can be 972, 864, 756, 648.

The total number of students in this school is ABC, and according to the question, 100a+10b+c-100b-10a-c=180, that is, 90a-90b=180 a-b=2

So a b

At the same time, the total number of people is a multiple of 36, that is, it is divisible by 4 and 9, so the mantissa is, empirically, and there are 972 if the conditions are met; 864；756；648。

100a+10b+c-100c-10b-a=18099a-99c=180

11*(a-c)=20

And 20 is not divisible by 11, so this question is wrong! 180 should be replaced by =integer != Integer: So one over 10 degrees and one over the other.

From the question, it can be concluded that the power of Zhang's family is more than 10, and the degree of more than 10 degrees is x, and the degree of Li's family is y<10

Then (10-y) * x * =

It is an integer from the question. So (the result is an integer.)

Use exhaustive methods. x is taken as 1, 2, 3, and 4 respectively, and only when x=3 is satisfied, then (10-y)=2

y=8, so the Zhang family is 13 degrees, and the Li family is 8 degrees.

Wrong question! Let the total number of people be 100a+10b+c, according to the meaning of the title

100a+10b+c-100c-10b-a=18099a-99c=180

11*(a-c)=20

And 20 is not divisible by 11, so this question is wrong! 180 should be replaced by 180

The first question 648, do not explain, the idea is to set the total number of people as abc, then abc-bac=180, the formula is erected to see c-c=0, a is definitely larger than b, and larger 2, from which we know that the combination of several possibilities a, b value is 97 86 75 64 53 42 31 20, a verification you will find that only 640 can be divisible by 36 and there is no remainder, and that number is 648, so c is 8, the answer is like this, not too specific, just write it on scratch paper.

The second question is too simple, and I am not happy to write it.

The third question, the diameter of the large circle is 20% larger than the diameter of the small circle, and the radius is the same, r=, the area of the large circle is several times that of the small circle is calculated by the formula of the area of the circle, what do you say is the answer?

1.648 people.

2.The Zhang family is 13 degrees, and the Li family is 8 degrees.

3.22 square centimeters.

1.648 or 864 or 972

2.The Zhang family is 13 degrees, and the Li family is 8 degrees.

3.22 square centimeters.

1. Set the hundred digit as x, the ten digit as y, and the single digit as z

The number of students is 100x+10y+z

The statistician writes it as 100y+10x+z

100x+10y+z-(100y+10x+z)=18090(x-y)=180

When x-y=2x 3, y can be greater than or equal to 1 to meet the condition.

Considering multiples of 36, 36*9=324 excludes 324*2=648 satisfying 6-4=2

Therefore, it should be 18 classes with a total number of 648.

2) Set the electricity amount to x, the electricity bill to y, Zhang's family is a, and Li's family is by= x 10

y= x>10

When a>10, b>10.

a-b= discord with the subject, discarded.

When a>10, b>10.

a-b= discord with the subject, discarded.

When a>10, b>10.

a=( It can be seen that b must be even, a can be rounded to b=2, a=(excluded.

Take b=4, a=(exclude.)

Take b=6,a=(exclude.)

Take b=8,a=(

Take b = 10, a = (exclude.

Therefore, Zhang's household electricity is 13 degrees, and the electricity fee = 10*

Li family 8 degrees, electricity =

3) S small = r 2 = 50 (square centimeters).

S large = r 2 = [r (1 + 20%)]2 = (s large - s small = square centimeters).

The large disc is 22 square centimeters larger than the small disc.

1722+10000=$11722

108x80%

3.One: 27x80%$two:

$A: If you choose the first method, you will get more interest.

1. 30, 20, let A be x, 50-x=2*

2. 18, 16, the first two sections are 49-15 = 34 kilometers, and the time is 10-(15 5) = 7 hours.

So, let us have the first section x km, x 6+(34-x) 4=7, or the inline equation x 6+(49-15-x) 4=10-(15 5).

3. Set the uphill x km, x 4+x 6+2*(9-x) 5=3+41 60, it's so troublesome, do it yourself.

Solution: 1) B's age in the current year is 50 (2+3)=10 (years) So B's current age is 10*2=20 (years), and A's is now 50- 20=30 (years) Answer, omitted (2) No.

The shared time of the first and second periods is 10-15 5=7 (hours) The first period is used as (49-15-4*7) (6-4)=3 (hours) Therefore, the first section.

The distance of the first and second sections is 6*3=18 (km) 4*(7-3)=16 (km) A, omitted.

3) Look at the question before asking the question!!

1.50-x-x=x-x 2 Answer A is 30 and B is 20.

2.49-15=34km 15 5=3h 10-3=7h Let the time of the first period be t 6t+4(7-t)=34 t=3h 3 6=18km

34-18=16km

3.The data came out not very well, and the final "distance" was changed to "speed".

Solution 1: Let the age of A be m and the age of B be n, then the system of equations is listed

m+n=50

n=2(m-n)

The solution is m=30 and n=20, that is, A is 30 years old and B is 20 years old.

The second problem is solved: Let the first section be a kilometer and the second section be b kilometer, then the system of equations can be listed

a+b=49-15 ..1 formula).

a÷6+b÷4=10-15÷5 ..2 formula).

Solution: a = 18 (km), b = 16 (km) i.e. 18 km for the first section and 16 km for the second section.

Problem 3: Calculate the hourly minute unit, 4 km hours = 1 15 km per minute, 5 km h = 1 12 km per minute. 3 hours and 41 minutes = 221 minutes.

If we set the uphill distance to m kilometers and the flat road to n kilometers, we can list the system of equations:

m+n=9 ..1 formula).

2｛（m÷1/15）+（n÷1/12）｝=221 ..2 formula).

Solve m=5 6 (km), n=49 6 (km).

[Fly up 2 times and square it].

There is xy=(x-2y) and the solution is x= y or x=4y, i.e., x y= 1 or x y=4

log(√2)(x/y)=lg(x/y)/lg(√2)

Solve one to get 0, and the other to get 3 [reverse use of the bottom change formula].

2.36=a 36=b is (2 36) + (1 36).

When simplifying, use [Bottom Swap Formula]: 2=( 2) ( 1) [Take an example of Bottom Swap Formula].

Here log 36 = lg36 lg3 log 36 lg4

2lg3=lg3 lg3 +lg4=lg(3 4)=lg36 is also used

After simplifying, merge similar items, and you will get lg36 lg36=1 [if you want to study by yourself, buy a reference book and take a look].

3.This solution equation is binary quadratic, huh? [The little girl doesn't know how to binary two drops].

1.According to the logarithmic algorithm: log a (m n) = log a (m) + log a (n), n log a (m) = log a (m n).

lgx+lgy=2lg(x-2y)

lg(xy)=lg(x-2y)^2

xy = x^2 - 4xy + 4y^2

x-y)(x-4y)=0

x=y or x=4y

lgx, lgy, lg(x-2y) make sense.

x>0，y>0，x-2y>0

x=4y can be derived from the logarithmic formula for log a m (b n) = (n m)log a (b).

Then: log( 2)( x y)=log [2 (1 2)] 4)=log [2 (1 2)] 2 2) = [2 (1 2)]log 2 (2) =4

2.According to the logarithmic definition: if a b = n (a 0, and a ≠1, n 0), then: log a (n) = b

3 a=4 b=36, then: a=log 3 (36), b=log 4 (36).

According to the logarithmic formula for dipping: log a (b) = [log c (b)] [log c (a)].

a=log 3 (36) = [log 10 (36)]/[log 10 (3)] =(lg36)/(lg3)

b=log 4 (36) = [log 10 (36)]/[log 10 (4)] =(lg36)/(lg4)

2/a + 1/b =2/[(lg36)/(lg3)] 1/[(lg36)/(lg4)]

2(lg3)/(lg36)] lg4)/(lg36)]

(lg9)/(lg36)] lg4)/(lg36)]

(lg9)+(lg4)]/(lg36)

lg36)/(lg36)

13.There are two unknowns, there is only one equation, and the equation cannot be solved.