Math problems are highly rewarded

It's too much trouble, wait, send it later.

I have written my own and found most of them on the Internet.

x+(x+1)+(x+2)+(x+3)=86

x+(x-7)+(x+7)+(x-1)+(x+1)=80

One question. Because the total price of 50 units is more than 90,000 yuan, then the two schemes are: A and B or A and C.

Plan 1: 25 units for A and 25 units for B. Deli, 8750 yuan.

Plan 1: 35 units for A and 15 units for C. Deli, 9,000 yuan.

This concentration should be the mass fraction, set to xkg.

Then x= is that the solute is unchanged when it is concentrated or diluted, so the two ends of the equation are the mass of the solute before and after dilution.

Dude, you made a mistake!

A ship traveled downstream from pier A to pier B, it took 2 hours, from pier B back to pier A to travel against the current, it took hours to know that the speed of the current is 3 kilometers per hour, find the speed of the boat in still water

Answer: Under normal circumstances, the boat returns according to the original route, so it can be considered that the round-trip distance of the ship is equalThus, the column equation is: 2 ( x 3 ).

Remove the parentheses to get 2x+6=

Move and merge , get.

The coefficient is reduced to 1 to give x=27

A: The boat has an average speed of 27 km/h

6: First question: Let's say Dad has been gone for x minutes.

180 m x min = 5 min x 80 m min + 80 m min x min

Solution: x=4

A: Xiao Ming's father caught up with Xiao Ming 4 minutes after departure.

The second question: 1000 meters - 80 meters minutes * 5 minutes - 80 meters minutes * 4 minutes.

280 meters A: Xiao Ming is still 280 meters away from the school.

After the encounter, we continue to drive to a distance of 100 km, which is equivalent to 100 km more than this section due to the same directional speed.

At the beginning, car A traveled 72*25 60=30 kilometers.

So the time it takes from this time to the meeting of the two cars = (360 + 100-30) (72 + 48) = 43 12

The total driving time of car A = 25 60 + 43 12 = 4 hours.

8: Solution: Set the number on the single digit to x

2x*10+x=x*10+2x+36

The solution is x=42x=8

So, the original number 84

9: Set the shortest strip to x

x：x+6=2：5

1.Hour casually flipped through a calendar, and saw that the sum of the 4 words in the upper row was 86, he told Xiao Gang the result, and asked Xiao Gang to say the first number of the four numbers?

1.Generally speaking, a critical point is a stationary point, a point with a zero first derivative, that is, a point with a zero slope, that is, a point where the tangent is parallel to the x-axis. So the first question is to choose iii(Do you understand that?) ）

2 Then, there is the relative extrema, which occurs when the first derivative is zero and the second derivative is not zero (it seems that this is the case, probably not only is the first derivative zero, but the monotonicity of the functions on both sides of this point also changes). So only x=-2 is, x=1 is not.

3Finally, the inflection point, which is the point at which the convex and concave properties of the function change, i.e., the point where the second derivative is zero, and the third derivative is not zero. If you look at it in the picture, it should be two. One is around -1 and one is around 1.

It's been a long time since I've done math and I've forgotten it. Hope it works a little bit for you. good luck。

I guess you're studying in the United States. It's pretty impressive.

Because the extrema is relative to the extremum point (the turning point between the increasing interval and the decreasing interval), there are 3 extremums.

a The critical point is the point at which the monotonicity of the function begins to change.

b The extreme point is the electricity at the peak and trough of the wave, and the left and right values are either larger or smaller than it, and there is one here.

c Inflection point The place where the convex curve and the concave curve are connected, the tangent of the curve is 45 degrees, and when the straight line is basically one, there seem to be two faces here.

It is said that it is the intersection point with the x-axis, and the first one is chosen.

(1).

The numbers in y are 1, 2, 3, 4, 5 times, respectively, and the multiplier relationship corresponds to the above x, so y increases with the increase of x.

2).From the first question, it can be seen that in the model where x and y conform to the proportional function, let y=kx, k=, i.e., y=(3)x=, then y=yuan.

y varies with x.

y=** of the goods is yuan.

(1) Y is linearly varied.

2) y=3) kilograms**=

What you can think of is this: change a 4-person room to a 6-person room, and for each room you change, you will add two beds. There were 15 people in total who had nowhere to live, so 8 houses had to be replaced to accommodate all 15 people, and the last one was not full.

The correct solution is: 15 divided by 6-4 to get it, but there is no half room, so it is 8 rooms.

So boys are 4*8+15=47 (people).

According to the title, if there are two more people in each room, 15 people should be allocated to the room, then the number of rooms can be speculated to be 15 2 rounded up, 8 rooms, then the number of boys is 4 * 8 + 15 = 47Verification: 6*8=48>47, then 7 rooms are full, and 5 people are in one room.

Solution: Suppose that the computer company purchased X sets of Type A computers, Y sets of Type B computers, and set Z of Type C computers from the computer company

It can be considered in the following three situations:

1) Only purchase A type computer and B type computer, and the system of equations can be listed according to the topic

6000x+4000y=100500,x+y=36x=

Solution. y=out of topic, should be discarded

2) Only purchase A type computer and C type computer can list the system of equations according to the topic

6000x+2500z=100500, x+z=36 x=3.

Z=333) only purchased B-type computers and C-type computers, and the system of equations can be listed according to the meaning of the topic:

4000y+2500z=100500, y+z=36x=7 solution.

Z=29 In summary, there are two options for the school to choose from, the first option is to purchase 3 A-type computers and 33 C-type computers; The second option is to purchase 7 B computers and 29 C computers

The number of students in class A is A, and the number of students in class B is B.

6+9（a-1）=13+8（b-1)

9a-3=8b+5

9a-8b=8

a=(8+8b)/9=8(b+1)/9

According to the title. 300<6+9（a-1）<400300<9a-3<400

303<9a<403

101 3 Wang Cracked A<403 9

300<13+8(b-1)<400

300<8b+5<400

295<8b<395

Only when b=44, a=40 is in line with the topic.

Therefore, there are 44 + 40 = 84 people in two shifts of A and B.