A question on a seventh grade math paper asks a scholar to help

Proof: Because the abc equilateral d is the ac midpoint.

So dbc=30° acb=60°

So ace=120°

And because cd=ce

So e=30°

So dbc= e db=de

And because dmb= dme

So DBM is all equal to DEM (AAS).

So m is the be midpoint.

Hello, lead a diagonal line to the midpoint of BC, the midpoint is denoted as F.

As can be seen from the above figure, dc=ce=ad, dc=1 2ac=1 2bc=bf=fc, and the angle acb is 60 degrees because the triangle abc is an equilateral triangle. In the same way, the angle dcf is 60 degrees, dc=fc. Then, the triangle DFC is an equilateral triangle, M is perpendicular to BC, M is the midpoint of FC, and FM=MC.

and fc=bf (f is the midpoint of bc), so, fc=ce=bf, that is, bf+fm=mc+ce.

Come to an end. <>

Is it good for you to explain the question?

Let Xiao Wang's speed be x meters and seconds, then Uncle will have a speed of 3 2x meters and seconds.

32（x+3/2x）=400

If we get x=5, then 3 2x=15 2

So Xiao Wang's speed is 5 meters and seconds, and Uncle's speed is meters and seconds.

Set up a few seconds for Uncle and Xiao Wang to meet.

15/2y-5y=400

Solution. y=160

So after 160 seconds, Uncle and Xiao Wang met again.

The track is 400 meters round, the speed of the track and field team members is 3 2 times that of Xiao Wang, and it takes 32 seconds to walk in opposite directions, and the speed of the two can be found to be: 400 32 * (2 5) = 5 meters and seconds, 400 32 * (3 5) = meters and seconds.

The next day, running in the same direction, is a pursuit problem, calculated by distance speed difference = time: 400 (seconds.

Let's take last year's profit to x

Then there is the equation: x 120 +1 = (x+50) 100 solution gives 100x +12000<=120x+60006000=<20x

x>=300 (10,000).

Last year's profit was at least 3 million.

Remove the brackets and extract the coefficients of the xy term, 3*(-3m)-1 2*7=0

9m-7/2=0

m=-7/18

The equation has to cancel out all the terms with xy, i.e., -9mxy, these two cancellations.

To offset, it is necessary to have a positive and a negative, that is, -9m= m=minus seven-eighteenths is not very clear, and the table is ......

Landlord, I'm the first, you must give it to me!!

The coefficients of the xy term are extracted.

9m+7/2)=0

m=-7/18

3（2x²-3mxy+y²）-x²+7xy-my²）

Multiply and open Merge the same terms 11 2x -(3m-7 2)xy + (1-m)y

Without xy, 3m-7 2 is equal to zero, 1-m is not equal to zero, m=7, 6

(1) Set the guaranteed wage as: x. The reward amount for each product is: YX+200Y=1800

x+180y=1700

x=800,y=5

2) The number of products sold by C: Z

800+5z≥2000

Calculated: z 240 pieces.

Solution: (1) Set a monthly basic guarantee salary of x yuan, and the reward amount of each product sold is y yuan. From the question, you can get:

x+200y=1800 solution: x=800

x+180y=1700 y=5

2) C sold a piece in the month. From the question, you can get:

800+5a is greater than or equal to 2000

Solution: a is greater than or equal to 240

So at least 240 pieces should be sold.

Solution: (1) The amount of rewards for each product sold:

1800-1700) (200-180) = 5 yuan of the employee's monthly basic security wage:

1800-200*5=1000 yuan.

2) C should be sold at least in the month:

2000-800) 5=240 pieces.

The specific calculation formula is not convenient to write I have stated in words, 1) the coordinates of point d are (3,1) because it is a rectangle ab is parallel and equal to cd by drawing it will be clear, point b and point c are symmetrical about the y axis, point d and point a are symmetrical about y, then the y coordinate value of point d must be 1, because ab is parallel and equal to cd, parallel to the y axis, point d and point a are symmetrical with respect to the y axis, then the x coordinate value of point d is 3, so the d coordinate is (3,1).

2) Because 1 unit per second moves horizontally, the y-coordinate value of the four points of the rectangle remains unchanged, and after only changing the x-coordinate value for 2 seconds, the coordinate change of the four points increases by 2, that is, the x-coordinate of the four-point is -1, -1, 5, 5, 5, 5, so the coordinates of the rectangle four-point are (-1, 1), (1, 3), (5, 3), (5, 1).

3) First calculate the area of the rectangle is 6 (the calculation formula is omitted), and then the column equation assumes that the coordinates of point c (m, n) then the coordinates of point d are (m-2, n+6) and the coordinates of point o are known (0, 0), then the area of the triangle can be listed by the formula 6=...... I forgot the specific formula, there should be this area formula in the book, I haven't read the book for several years, I have forgotten it, you must give me a point, I read the information Oh, there is no wealth value.

, 1) AB is parallel to the y-axis, BC is parallel to the x-axis, and the drawing comes out.

2.Add the ABCD coordinate X coordinate by 2 and you're good to go.

a1(-1,1)

b1(-1,3)

c1(4,3)

d1(4,1)3.

(2,1).

1,1). b -1,3 c 4,3 d 4,1

3.First, find the area of ABCD as 10. Look at the invariants again, and then find them.

(1)d(2,1)

2)a1(-1,1)

b1(-1,3)

c1(4,3)

d1(4,1)

3) What is the meaning of the third question? Please add more, I will revise the answer.

For a clearer representation, I drew a diagram).

The exam is a test and assessment of your usual learning, don't have any shortcut thoughts, to study hard down-to-earth, when you get a high score through your own hard work, your heart will be the sweetest, if you get the test paper before others, even if you get a high score in addition to satisfying vanity, what is the meaning of it for you? You are still young, study hard, and you will definitely be able to get into your ideal middle school and university! I wish the title of the gold list!