The unit price of a commodity is reduced from 200 yuan to 128 yuan after two successive price cuts

The unit price of a commodity is reduced from 200 yuan to 128 yuan after two successive price cuts

Let X be the average percentage of each price reduction of this product. According to the meaning of the question, we get: 200 (1-x) 2 = 128. The solution is: X1 = 0.2 = 20%, X2 = 1.8 = 180% (rounding off). A: the average percentage of each price reduction of this drug is 20%

Let f (x) = LNX + ln (2-x) + 1 find the domain of definition and monotone interval of function
ah

1, first find the domain. X is greater than 0, and 2-x is greater than 0. So 0

Quadratic equation of one variable
5(x^2-x)=3(x^2+x)

5x^2-3x^2-3x-5x=0
2x^2-8x=0
x^2-4x=0
X = 0 or x = 4

The price of a computer increased by one tenth in the first ten days of October and one eleventh in the last ten days of October. Now the price is 5000 yuan. The current price is the same as the original price
The price of a computer increased by 10% in the first ten days of October, and by 11% in the last ten days of October. Now the price is 5000 yuan. How much is the difference between the current price and the original price? The answer is not to copy. If I want a symbol like × / x, I'd better explain it in a hurry!

The original price is: 5000 ^ (1 + 1 / 11) ^ (1 + 1 / 10)
=5000 △ 6 / 5
=12500 yuan / 3
Difference: 5000-12500 / 3 = 2500 / 3 ≈ 833 yuan
If you don't understand, you can ask
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Calculation: square of - 2 ×√ 8 + 3 √ 2 (3-2 √ 2) - √ 1 / 2

4 root 8 + 9 root 2-12-2 root 2 = 4 √ 8 + 8.5 √ 2-12

Algebra
Given a ^ 2-4a + 1 = 0, then the value of (2a ^ 5-7a ^ 4 + A ^ 3-11a ^ 2 + 7a) / (3a ^ 2 + 3) is_________ .
Note:

Methods: using a ^ 2-4a + 1 = 0, get a ^ 2-4a = - 1, and then reduce the higher power to power
2a^5-7a^4+a^3-11a^2+7a
=2a^3(a^2-4a)+a^4+a^3-11a^2+7a
=-2a^3+a^4+a^3-11a^2+7a
=a^4-a^3-11a^2+7a
=a^2(a^2-4a)+3a^3-11a^2+7a
=3a^3-12a^2+7a
=3a(a^2-4a)+7a
=4a
=a^2+1
(2a^5-7a^4+a^3-11a^2+7a)/(3a^2+3)=1/3

A commodity is priced at 20% of the profit and finally sold at 80% of the price. As a result, each commodity loses 56 yuan. What is the cost price of this commodity
A commodity is priced at 20% of the profit and finally sold at 80% of the price. As a result, each commodity loses 80 yuan. What is the cost price of this commodity

Set the cost as X Yuan
The price is x * (1 + 20%)
The selling price is x * (1 + 20%) * 80% = x * 1.2 * 0.8
x*1.2*0.8-x=-56
0.4x=56
X = 140 yuan
The cost of this product is 140 yuan

For a two digit number, the sum of the ten digit number and each digit is 11. If the ten digit number is replaced with a single digit number, the two digit number will be 63 larger than the original number,
For a two digit number, the sum of the ten digit number and each digit is 11. If you exchange the ten digit number with the one digit number, the two digit number will be 63 larger than the original number. Find the two digit number
Please write the process

Let the one digit number be x, then the ten digit number be 11-x. from the meaning of the title, we can get (10x + 11-x) - (110-10x + x) = 63
X = 9, the two digit number is 29

There are two ways to charge for surfing the Internet in a certain place. Users can choose one of them: (a) time system: 2.8 yuan / hour, (b) monthly system: 60 yuan / month. In addition, communication fee of 1.2 yuan / hour will be charged for each way of surfing the Internet. (1) which way is more reasonable for a user to surf the Internet for 20 hours? (2) A user has 120 yuan for surfing the Internet (one month), which way is more cost-effective? (3) Please design a scheme for users, so that users can choose a reasonable way to access the Internet

(1) A: time system: 20 × (2.8 + 1.2) = 80 (yuan) B: monthly system: 60 + 20 × 1.2 = 84 (yuan) ∵ 80 ∵ 84, it is more cost-effective to choose the time system. (2) 120 ∵ 2.8 = 3007 (hours) (120-60) ∵ 1.2 = 50 (hours) because 3007 hours ∵ 50 hours, it is cost-effective to choose the monthly system; (3) set the user to surf the Internet for X hours, the cost of the two ways is the same（ 2.8 + 1.2) = 60 + 1.2x, and the solution is x = 1507. When the user's online time x > 1507, the monthly system is selected; when the user's online time x < 1507, the hourly system is selected; when the user's online time x = 1507, the hourly system is the same as the monthly system

As shown in the figure, if the quadrilateral ABCD is a diamond, the parallel line passing through point a as BD intersects the extension line of CD at point E, then the following formula does not hold ()
A. DA=DEB. BD=CEC. ∠EAC=90°D. ∠ABC=2∠E

∵ quadrilateral ABCD is rhombic ∥ ab ∥ CE, ab = Da = DC = BC, ∠ ABC = 2 ∠ abd, BD ⊥ AC ∥ oad + ∠ ODA = 90 ° and ∵ BD ∥ AE, ∥ quadrilateral ABDE is parallelogram, ∠ ead = ∠ OAD ∥ AB = Da = De, ∠ e = ∠ abd ∥ ead + ∠ ODA = 90 ° that is ∠ EAC = 90 °, ABC = 2 ∠ e, so B is not tenable