The extremum of higher number. Y = 2x to the third power - 6x square - 18x + 7

The extremum of higher number. Y = 2x to the third power - 6x square - 18x + 7

The derivative is 6x ^ 2-12x-18
Let it be zero, and the solution is x = - 1 or 3
Substituting y = 17 or - 47
The second derivative is 12x-12. When x = - 1, the maximum value is less than zero, and when x = 3, the minimum value is greater than zero
The maximum is 17
The minimum value is - 47

18x cubic y square x 12x square y square - 2x cubic y

What are you doing? Factoring?
18x cubic y square x 12x square y square - 2x cubic y
=18x³y²+12x²y²-2x³y
=2x²y(9xy+6y-x)

Warehouse A and warehouse B need to deliver cement to a and B. It is known that warehouse a can transfer out 100 tons of cement and warehouse B can transfer out 80 tons of cement;
70 tons of cement is needed in a and 110 tons in B. the distance and freight from two warehouses to a and B are shown in the table below
Distance (km) freight (yuan / ton * km)
Transport out of warehouse A, warehouse B, warehouse A, warehouse B
arrive
A ground 20 15 12
B ground 25 20 10 8
(1) Suppose x tons of cement transported from warehouse A to place a, find the algebraic formula of total freight y (yuan) with respect to X (tons) and the value range of X;
(2) Design a deployment plan to save the total freight
Distance (km) freight (yuan / ton * km)
Transport out of warehouse A, warehouse B, warehouse A, warehouse B
arrive
A ground 20 15 12
B ground 25 20 10 8

Methods: (1) set up a warehouse to transport x tons of cement to a warehouse, according to the meaning of the title, y = 12 × 20x + 10 × 25 (100-x) + 12

It is known that a, B and C are the three sides of a triangle. Let's try to explain that the equation B + X (B + C-A) x + C = 0 has no real root
Please don't send random code, Du Niang doesn't translate... So it's like me to write Chinese characters

Car a can travel 20 kilometers in 28 minutes, and car B can travel 25 kilometers in 40 minutes. Which car is faster per minute?
Hurry up, hurry up! You need the formula and the answer
Be more specific

20 / 28 = 5 / 7, 25 / 40 = 5 / 8, 5 / 7 > 5 / 8, car a is fast

In Volume 2 of the fifth grade elite PHS (Beijing Normal University), 60 pages of Mathematical Olympiad questions
A group of mowers should cut two pieces of grass, the big one is twice as big as the small one. All the team members first cut a large piece of grass in half a day, and then half of it will be separated in the afternoon, half of it will still be left on the big grass, and the big grass will be cut in the evening. The other half will go to the small grass to cut, and there will be a small piece left in the evening, How many people are there in this group? (no matter how long it is in the evening)
I can't understand the way you use~
I divide (1 + 2) = 1 / 3 by arithmetic
1 / 3 times 2 = 2 / 3
1/2-1/3=1/6
1 / 6 divided by 2 = 1 / 12
2 / 3 divided by 1 / 12 = 8 (person)
I don't know if I can understand it
Because the time of mowing in the morning is twice as much as that in the afternoon, the big grassland is regarded as "1"
Use: 1 divided by (1 + 2) = 1 / 3, 1 / 3 is the decimal, which is the effect of half people in the afternoon ~ then 2 / 3 in the morning
So... Big grassland is twice as big as small grassland. In other words, big grassland is regarded as unit "1" while small grassland is 1 / 2
The topic said that the people who cut the big grass in the afternoon are the same as the people who cut the small grass in the afternoon. So the people who cut the big grass in the afternoon cut 1 / 3, and the people who cut the small grass also cut 1 / 3
We find that the small grassland is 1 / 2 of the large grassland. If we cut 1 / 3, then the remaining 1 / 2-1 / 3 = 1 / 6
1 / 6 is the effect of a person in a day. However, it is said that 1 / 6 is divided by 2 = 1 / 12 in half a day
But it's only half a day for one person. If you want to figure out the number of people, divide 2 / 3 by 1 / 12 = 8~

Solution 1: suppose there are x mowers in total. If all the mowers work for one day and one mower works for one day, it will take x + 1 day for one person to finish cutting two pieces of grassland. It will take (x + 1) / 3 days for one person to finish cutting one third of two pieces of grassland. On the other hand, if x / 2 mowers work for 1 / 2 days for one person, it will take (x / 4) + 1 day for one person to finish cutting a small piece of grassland

Black heart boss designed a watch, like the standard time every 71 minutes, the minute hand coincides with the hour hand. Master Zhang works 8 hours a day according to the boss's watch. The boss stipulates that the salary in time within 8 hours is 6 yuan, and the overtime salary outside 8 hours is 2 times of the original salary. How much less does black heart boss pay you every day?
Make the standard time coincide with the hour hand every 72 minutes,

72-60 more per hour = 12 minutes
8 hours is 8 * 12 = 96 minutes
Overtime pay 6 / 60 * 96 * 2 = 19.2 yuan
That is 19.2 yuan less

The tangent equation of curve f (x) = 2x2-1 at point (1, f (1)) is______ ．

If f (1) = 2-1 = 1 and f ′ (x) = 4x, then f ′ (1) = 4, the tangent equation at point (1,2) is Y-2 = 4 (x-1), that is, 4x-y-2 = 0, so the answer is 4x-y-2 = 0

A batch of goods can be transported by car 18 or 4 times at a time___ If the goods weigh 116 tons, they have already been shipped away___ Tons

3x + 1 + X + 1 / 1 > x + 1 / 1 + 5x-1
3x + 1 + (1 / x + 1) > (1 / x + 1) + 5x-1
I want to help you today!
3x + 1 + (x + 1) 1 / 2 > (x + 1) 1 / 2 + 5x-1

3x + 1 + X + 1 / 1 > x + 1 / 1 + 5x-1
First move the term, 3x + 1 > x + 1 / 1 + 5x-1-x + 1 / 1
The results show that 3x + 1 > 5x-1
Transfer the term and get 3x-5x > - 1-1
Get, - 2x > - 2
x