The original price of a product is 50 yuan, and the price has been reduced by 10% twice in a row. What's the price

The original price of a product is 50 yuan, and the price has been reduced by 10% twice in a row. What's the price

The first 10% reduction is 45 yuan, the second 10% reduction is 40.5 yuan, and the final price is 40.5 yuan

What is the domain of the function f (x) = 1 / ln (2x-1)
I am very poor in mathematics, there may be some very stupid questions, please help experts

True number 2x-1 > 0
x>1/2
Denominator ln (2x-1) ≠ 0
2x-1≠1
x≠1
Domain (1 / 2,1) ∪ (1, + ∞)

There are 100 peach trees in an orchard, and each peach tree bears 1000 peaches on average. Now we are preparing to grow a variety of peach trees to increase the yield. The experiment found that for each variety of peach trees, the yield of each peach tree will decrease by 2, but the number of peach trees can not exceed 100. If we want to increase the yield by 15.2%, how many peach trees should be planted?

Suppose there are many x trees, then (100 + x) (1000-2x) = 100 × 1000 × (1 + 15.2%) (0 ＜ x ＜ 100), the result is: x2-400x + 7600 = 0, (x-20) (x-380) = 0, the solution is X1 = 20, X2 = 380

If a commodity is sold at a reduced price according to the season, if it is reduced by 10% at the current price, it will still make a profit of 180 yuan. If it is reduced by 20%, it will lose 240 yuan. How much is the purchase price of this commodity?

Suppose the current price is x yuan, from the meaning of the question: (1-10%) x-180 = (1-20%) x + 240, & nbsp; & nbsp; & nbsp; & nbsp; 90% x-180 = 80% x + 240, & nbsp; 90% x-180-80% x = 80% x + 240-80% x, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 10% x-180 = 240, & nbsp; 10% X

There are several significant numbers of 3.14 × 10 to the fourth power

Three, that's three, one, four, three
But if it's 31400, it's five

A mathematical algebra problem
If x + y = the reciprocal of X + the reciprocal of Y and is not equal to 0, then xy =?
... is x + y = x / 1 + Y / 1

X + y = 1 / x + 1 / y is divided into x + y = (x + y) XY
Because x + y is not equal to 0, both sides of the equation can be divided by X + y
So xy = 1

The use value of goods is () a, the result of abstract labor B, the material content of social wealth C, the result of concrete labor
D. The social form of social wealth under certain social relations
E. Material undertaker of exchange value

B/D/E

For a two digit number, the number of a single digit is twice that of a ten digit number. If the ten digit number is transposed with the number of a single digit, then the number obtained is 36 times larger than the original two digit number, and the two digit number can be obtained

If ten digits is x, the single digit is 2x
Original number = x * 10 + 2x = 12x
Variable = x + 2x * 10 = 21x
21X-12X=36
X=4
4*2=8
The original number is 48

1. The speed of train a is 60 km from a to B, and that of train B is 90 km from B to a at the same time. It is known that the distance between the two places is 200 km. How far is the place where the two trains meet from a?

Let the time of meeting be X
（60+90）*X=200
X = 4 / 3 hours
The distance between location a and location a is 60 * 4 / 3 = 80 km
A: the place where the two cars meet is 80 kilometers away from a

As shown in the figure, in square ABCD, e and F are the midpoint of AB and BC respectively

Let CE DF intersect o
Angle B = angle c = 90 degrees
CB=CD
CF=FB=1/2BC=1/2AB=EB
So the triangle CEB is equal to the triangle DFC
So angle CEB = angle DFC
Because angle BCE + angle CEB = 90 degrees
So angle DFC + angle CEB = 90 degrees
So the angle COF = 90 degrees
So CE vertical DF