A new batch of computers of the same model are purchased in a shopping mall, and the price is increased by 40% according to the purchase price (that is, the price indicated on the price plate). In order to promote sales, the shopping mall gives a 20% discount to the computers (20% discount means that the actual price is 80% of the price). Each computer can still make a profit of 420 yuan, so the purchase price of each computer of this model is______ Yuan

A new batch of computers of the same model are purchased in a shopping mall, and the price is increased by 40% according to the purchase price (that is, the price indicated on the price plate). In order to promote sales, the shopping mall gives a 20% discount to the computers (20% discount means that the actual price is 80% of the price). Each computer can still make a profit of 420 yuan, so the purchase price of each computer of this model is______ Yuan

Let the purchase price of this model of computer be x yuan. According to the equation, we get: (x + 40% x) × 0.8-x = 420, and the solution is: x = 3500. The purchase price of this model of computer is 3500 yuan

A new batch of computers of the same model are purchased in a shopping mall, and the price is increased by 40% according to the purchase price (that is, the price indicated on the price plate). In order to promote sales, the shopping mall gives a 20% discount to the computers (20% discount means that the actual price is 80% of the price). Each computer can still make a profit of 420 yuan, so the purchase price of each computer of this model is______ Yuan

Let the purchase price of this model of computer be x yuan. According to the equation, we get: (x + 40% x) × 0.8-x = 420, and the solution is: x = 3500. The purchase price of this model of computer is 3500 yuan

A shopping mall sells 1980 goods at a 20% discount on the price, and still makes a profit of 198 yuan. The price is calculated according to the equation

Set the price as X Yuan
x×80％＝1980＋198
80％x＝2178
x＝2178÷80％
x＝2722.5

If a department store sells a commodity with a purchase price of 1980 yuan at a 20% discount on the price, it can still make a profit of 10%, then the price of the commodity is ()

If the price is set as X Yuan, then according to the meaning of the question, it is 0.8x-1980 = 0.1 * 1980, and the solution is x = 2722.5 yuan

In the set {1,2,3,4 10} Three numbers are randomly selected from the list, so that the three numbers are in an increasing equal proportion sequence. How many are these sequences

The common ratio Q equals q = 1 / 2 (1,2,4); (2,4,8)
Common ratio Q equals q = 1 / 3 (1,3,9)
Common ratio Q equals q = 2 / 3 (4,6,9)
Conversely, q = 2 and q = 3 have four
So the number of sample ratio sequence is 8

The product of three numbers is 512. If the first number and the third number are subtracted by 2 respectively, they will be equal difference series. Find the three numbers

Let three numbers be a, B, C in turn. According to the meaning of the question, ABC = 512 ∵ the three numbers form an equal ratio sequence, ∵ B2 = AC, ∵ B3 = 512, B = 8. Let the common ratio of the three numbers be t, then a = 8t, C = 8t. The first number and the third number are reduced by 2 respectively. The later number sequence becomes 8t-2, 8, 8t-2 ∵ the new number sequence becomes an equal difference number sequence ∵ 16 = 8t-2 + 8t-2. Arrange 2t2-5t + 2 = 0, obtain t = 2 or 12. When t = 2, a = 4, C = 16, the three numbers are 4, 8, 16 When t = 12, a = 16, C = 4, the three numbers are 16, 8, 4

The set sequence {1}, {2,3}, {4,5,6}, {7,8,9,10} is given. Let Sn be the sum of the elements in the nth set, then what is S21?

This According to several sets in the title, there is one element in the first set, two elements in the second set, and three elements in the third set So there are n elements in the nth set, and the first element in the nth set is smaller than the last element in the Nth-1 set

Sequence, set, probability
（1） . a, B are real numbers, set M = {B / A, 1}, n = {a, 0}, F: X → x means that the value of a + B is equal to (...)
...A,1.B,0.C,-1.D±1
（2） If f (1) > 1, f (2) = (2a-3) / (a + 1), then the value range of real number a is (...)
...A,a2/3.B,-1

In the first question, because the element X in the set M is still X in the set n, so a = 1, B / a = 0, so B = 0, so a + B = 1, choose a
Second, since f (x) is an odd function defined on R with a period of 3, f (- 1)

What is set {0}____ Sequence? Why?

The set {0} is a constant sequence, which is a set of elements with 0. The elements in it constitute a constant sequence, because there is only one constant 0 in this sequence, which constitutes a set and a sequence

I know the difference between a sequence and a set
For example, the set operator set has the formula 2 ^ n (n is the element in the set)
What formulas are available for these two problems in the sequence?
:
It is known that the sequence {AK} K belongs to the closed interval from 1 to 4, and K belongs to n*
Each item of is an element in the set {1,2,3,4},
If n different sequences can be formed, then the value of n is?
A 2
B 24
C 256
D indeterminate
It is known that the sequence {AK} K belongs to the closed interval from 1 to 4, and K belongs to n*
The items of are different from each other, and they are all elements in the set {1,2,3,4},
If n different sequences can be formed, then the value of n is?
A 2
B 24
C 256
D indeterminate
Waiting for ing
By the way, please explain my two examples
Choose your best

Sequence refers to the set of numbers arranged together according to certain rules
Set is just putting numbers together, no rules