Math Problem Clarification Process Rush Rush Hurry

There are x people who can list the equation from the title: 5x+5=7x-13, and the solution is x=9, so there are 5*9+5=50 copies.

It can be seen that 29 people crossed the river, and one was a boatman.

Then each time three people are transported 29 3 = 9 and more than 2 will take a total of 10 times.

First of all, find out how many people are divided.

According to the question, each person adds 2 books, and the homework book will increase (13 books + 5 books) 18 books, so it can be calculated that there are 18 2 = 9 people.

Then count how many homework books there are.

5*9+5=50 copies.

1+(30-4) (4-1) is about 10 times.

The first question has x people, 5x+5=7x-13, x=9, and 5x9+5=50 workbooks.

The second question is to cross the river ten times.

Solution: There are x people, each person is divided into 5 books, and the remaining 5 books indicate that there are 5x+5 books; If each person is divided into 7 books, and there are 13 books missing, it means that there are 7x-13 books, and the two formulas are equal to 5x+5=7x-13, and the solution is x=9, and x+5=50 books are substituted.

Solution: Because the boat can carry four people at a time, because the boat has to drive back to the other side, so it can only carry three people each time, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, a total of 19 times, I think it is 19 times, because it is counted twice back and forth. If you don't count the number of times, it's 10 times.

The river crossing is: 30 3 = 10 (times) 10 2 minus 1 = 19 times Answer: 19 times.

I'll just do that.

2c, according to the difference between any two sides of the triangle is less than the third side, it can be known: the first absolute value is a positive number, do not change the sign, the second is a negative number, all of them must be changed, after simplification, it is 2c, hope!

The three sides of a triangle should be thought of – the sum of any two sides of the triangle is greater than the third side.

So a+c-b>0 and a-(b+c)<0

Remember to go to the absolute value - the absolute value of a negative number is its opposite, so |a-b-c|＝b+c-a

a-b+c|+|a-b-c|

a-b+c-a+b+c2c

a-b+c|+|a-b-c|=a+c-b+b+c-a=2c

When the absolute value is obtained, the ...... is made according to the fact that the sum of the two sides of the triangle is greater than the third side

（1）。Substituting x=0 and y=0 into y=kx +2 3(2+k)x+k +k, you can get the value of k. The equation for the parabola is specific.

2）。With point a, we make the symmetry point A1 with respect to the y-axis. Connect a1b and cross the y-axis at point p.

Then p is what is sought. The reason for this is [specular reflection]. Or the circumference of the triangle PAB is equal to the circumference of the triangle PA1B.

3）。The essence is to find the heart of the triangle and use the distance formula from the point to the straight line. In fact, it is to find the coordinates of the intersection of two inner angle bisectors, (this method seems to save a little bit of trouble.) ）

Since the parabola is brought into after the origin (0,0), k=-1 is obtained, and k=0 does not meet the parabola, which is omitted.

After getting k, bring in the parabola.

Go to the parabolic analytic equation and then you have to make it into a standard equation or find the two derivatives to get the turning point and you can find b

..Too much.

then walking to or from work is required

When I go to work and take the car, I can't share it on the road after work.

Then it takes to get to work by car: hours.

Therefore, it takes an hour to travel back and forth by car.

A: Master Zhang takes a car to and from the road, and it takes hours on the road.

2. Solution: Take a car to and fro, and the whole journey takes 10 minutes.

It takes 5 minutes to get to or from the bus.

I went to school and took the bus, and walked home for a total of 36 minutes.

It takes 36-5=31 minutes to walk home.

Therefore, it takes 31 + 31 = 62 minutes to walk round trip.

A: It takes 62 minutes to walk round trip.

3. Solution: Take a car to and fro, and the whole journey takes 30 minutes.

It takes 15 minutes to get to or from the bus.

I went to school and took the bus, walked home, and shared time on the road.

It takes hours to walk home.

Therefore, it takes 1+1=2 hours to walk round trip.

A: If it takes 2 hours to walk round trip.

1. Getting to work by car is faster than walking: hours.

So all by car, 2 hours faster, that is, hours.

2. Walking is slower than taking a car: 36-10=26 minutes.

So all walking: 10 + 26 * 2 = 62 minutes.

3. Same as 2 questions, 85-30=55 minutes.

So, 30 + 55 * 2 = 140 minutes.

1. Half-way car ride saves time = average walking time for round trip - time to go to work and get off work.

= 1 (hour), time saved by car ride = 2 time saved by car ride = 2 (hours) by car ride

Full ride time = full walking time - full ride time saved = - 2 = hours).

Therefore, the round-trip ride time is hours.

2. Half-walk takes more time than taking a car = 36 - 10 = 26 (minutes).

Round-trip walk time is more than car ride = 2 Half walk time is more time than car ride = 52 (minutes).

Round-trip walking time = round-trip travel time + round-trip walking time = 10+52=62 (minutes).

3. Walking time to school and going home by car 2 = time to and from the bus + time to walk back and forth.

So: Round-trip walking time = Round-trip walking time to school and bus home 2 - Round-trip bus ride time = 2 - 30 60 = 2 (hours).

1. Because if you walk to and from the car, the distance and time are the same, so the one-way walking time = and the walking plus car share the hour, so the one-way time to take the car = , so the round-trip time =

2. Same as 1, it takes 10min to take the car back and forth, so the one-way ride time = 10 2 = 5min, and the walk plus the car shares 36min, so the one-way walking time = 36-5 = 31min, so the round-trip walking time = 31 * 2 = 62min

3. As with , it takes 30min to take the car back and forth, and the one-way ride time = 30 2 = 15min, and the car plus walking time is a total of 75 minutes, that is, 75 minutes, so the one-way walking time = 75-15 = 60min, so the walking round-trip time = 60 * 2 = 120min

1. Hours.

Round-trip walking = hours, you can know one-way walking = hours. Take a car to work + walk to work (one-way walk =, you can know that one-way car = hours, so take a car back and forth =.)

Minute. By car + walking = 36, by car + by car = 10, it can be seen that by car = 10 2 = 5, walking = 36-5 = 31, so walking back and forth = 2 * 31 = 62 minutes.

Hour. Car + walk =, car + car = unit to be unified), car = , walk = 1, so walk + walk = 1 * 2 = 2

1) Use the arc length formula and the inner angle and formula of the triangle and the quadrilateral to substitute the calculation;

2) Calculate by using the formula of the inner angle of the polygon and the formula of the arc length Answer: Solution: (1) It can be obtained by using the formula of the arc length.

n1 1180 + n2 1180 + n3 1180 = because n1 + n2 + n3 = 180°

In the same way, the quadrilateral = n1 1180 + n2 1180 + n3 1180 + n4 1180 = 2, because the inner selling angle and grip of the quadrilateral are 360 degrees;

2) n arcs = n1 1180 + n2 1180 + n3 1180 + n4 1180 + ....=n-2)×180π×1180=（n-2）π．

1) 180 * 1 180 = ,2 * 180 * 1 180 = 2, therefore, the sum of the arc lengths of the 3 arcs in Figure A is Lu Da ( The sum of the arc lengths of the 4 arcs in Figure B is ( 2

2)(n-2)180 *1 180=(n-2), therefore, the sum of the arc lengths of n arcs in Figure C is =(n-2),

1) Because the inner angles of the triangle and 180 are half of the circle, the three arcs are combined into a semicircle. Therefore, the length 2 r 2=1 = 2)2 is the same as the blind call. The quadrilateral 360 is exactly put together into a circle with a length of 2 r=2

Chain pose 3) n The same is true.

Original. Thank you.

a b c x 100-x

d 90-x x-40:60-(100-x)

This is the allocation table, I believe you should understand it.

This gives w=10x+4900 (amount. This is my rough calculation, if there is any error, bear with me)

The value of the independent variable x can be 40 x 90

How did this 40 come about-= you look at b-d, x-40 in the distribution table

If it is less than 40 and it becomes negative, it is not in order. (Actually, this is just my personal statement, to do this kind of problem, you should look at the smallest number of x in the distribution table, and if it can become 0, you should take the smallest number, for example: 100-x is the smallest value of x in this distribution table to make this formula 0, so x should take 100).

So, this 40 is the smallest value in the allocation table, which is the smallest value in the range of the value of the independent variable x.

And the same is true of 90, this is the largest number in the distribution table, you don't look at the 100-x, think that this x should take 100, you look at it, the 90-x if x takes 100, this becomes negative.

So, it's 40 x 90

I don't know what you think, if there are any mistakes or omissions, please point me out.

2.Set up X tons of fertilizer from county C to county A, the total freight = 35x + 40 (90-x) + 30 (100-x) + 45 (x-40).

10x+5100

30≦x≦90

The total freight is the lowest, x = 30, 30 tons of fertilizer is transported from county C to county A, and the total cost of the lowest draft type is 5400 yuan.