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i) A3=10-d, a6=10+2d, a10=10+6d from a4=10

a3, a6, a10 in proportional series.

Therefore, there is (10+2d)2=(10-d)(10+6d)d=1an=a4+(n-4)d=n+6

2)s20=1+2+3+..20+6*20 hope to help, hope, I wish you progress in your learning,

1) Let the tolerance be d, then.

a3=10-d, a6=10+2d, a10=10+4dso, (10-d)(10+4d)=(10+2d)(10+2d)d(d-1)=0

So d = 1a1 = 10 - 3d = 7

So an=n+6

2) Let the sum of the first n terms of an be an, then.

an=n(n+13)/2

Because the second half of bn is a proportional series, bn=-1+2 to the nth power.

So sn=an+bn

AE is not parallel to BC, reason: find a random point E so that AE is not parallel to BC, connect CE, find the midpoint of CE through this midpoint as a perpendicular line, and intersect with the extension of BA at point D, connect CD, CE. Then remove the perpendicular line.

The figure made at this point is consistent with the title, but AE is not parallel to BC.

Money in the hands of dad mom sellers.

0 500 500 0 Not borrowed.

1000 0 0 0 Money borrowed.

30 0 0 970 Purchased.

10 10 10 970 Repaid.

1) (Explanation) And the calculation of the question is like this.

Equivalent to 500 + 500 - 10 = 990

And this is completely inconsistent with scientific and mathematical logic!!

It means that at the beginning only 490 was borrowed from the parents separately.

It can also be expressed as 490 + 490-970 = 10, and the shift item has to be 490 + 490-10 = 970, which is the same as the title.

2) There is also a three-person hotel, the same is true (I believe everyone knows the title, because the question seems to be the ancestor).

Let's just repeat it here.

Three people lived in the hotel, one made up 10 yuan for a total of 30 yuan to the waiter, and later the waiter knew that the special offer was only 25 yuan, so he gave the boss 25 yuan, so the waiter was greedy for 2 yuan, and returned 3 yuan to the three people. The three of them shared 1 yuan equally. In this way, 3x9+2=29 yuan, and one yuan?

2) (Explanation) Question Algorithm: 3 (10-1) + 2 = 29

This calculation means that the guest pays 9 yuan at the beginning, and the wrong place is 3x9=27 yuan, 25 yuan to the boss, and 2 yuan to the waiter, so it should be 27-2=25, but it becomes 27+2=29).

Correct algorithm: (when only 9 yuan is paid, 3x9 = 25 + 2) (when 10 yuan is paid, it is as follows).

Guest a b c waiter owner.

10 10 10 0 0 Pool.

0 0 0 30 0 Pay.

0 0 0 5 25 The boss collects money and pays back 5 yuan.

1 1 1 2 25 3 yuan, greedy 2 yuan.

If you just want to get the right answer, you can get a clear answer by listing it step by step, like I did.

If you want to know why the question is wrong, you have to think about it.

Try it with the accounting method of debit accounting, this is not a mathematical problem...

Borrow: 1000 in cash

Credit: Liabilities 500+500

Borrow: Leather Shoes 970

Credit: Cash 970

Debit: Liability 20

Credit: Cash 10+10

Therefore, assets = cash 10 + leather shoes 970 = 980

Liabilities = original liabilities 1000 - repaid 20 = 980

Assets = Liabilities.

You should have noticed that in the original text, the last use of liabilities 980 + cash items in assets 10 = 990 is itself wrong.

970 = 485 + 585, 10 yuan for Dad, 10 yuan for Mom, and 10 yuan for yourself.

Owe Dad 490Owe mom 490 from?

That's not how it works, it's 1000, it's not wrong, but if it's separated, buying leather shoes should be.

970 = 485 + 485 That is, 485 from each of the money borrowed by your parents, so that you have 30 yuan left for yourself.

10 yuan each, that is, 495 + 495 = 990 Don't explain it.

He borrowed 1000 from his parents... But I paid back 20 ,。。 after buying it So it's equivalent to borrowing 980 yuan.

The 970 yuan for buying shoes plus 10 yuan for yourself is also 980 yuan for the rest of the ,,,.

You shouldn't think like that, you've borrowed a total of 980 yuan, and you used 970 yuan to buy shoes, and you're right to have 10 yuan left.

Actually, there is nothing wrong with that! It's just that the mindset thinks that there is an extra 10 yuan, but in fact, this 10 yuan has been counted once in 970 yuan, and it has been counted again in 30 yuan, of course, it has to be more.

It's not to add my ten yuan, here is a change of concept, it should be the money owed to my parents minus the money I have left is equal to the money of leather shoes, 580-10 = 570.

It's not about math, it's a brain teaser.

y=1 2【sin(2x- 3)-sin(x-x+ 3)】=1 2sin(2x- 3)-4/3 of the root number, period t = maximum 2x- 3= 2 times (4 k -3) 2 k = (1,2,3) minimum 2x- 3=3 2 times (4k-1) 2 k = (1,2,3

y=sin(x－π/3)cosx=cosx[(1/2)sinx－(√3/2)cosx]=(1/4)sin2x－(√3/4)[2cos2x＋1]=(1/2)sin(2x－π/3)－√3/4。The maximum is (1 2) 3 4, where 2x 3 = 2k 2 (find x), and the minimum is (1 2) 3 4, where 2x 3 = 2k 2.

y=cosx

then y'=-sinx

The slope of the tangent is y'

So k=-sinx>0

sinx<0

So

Solution: =lim(n)丨an+1 an丨=(1 2)lim(n)n+1) (n+2)=1 2. Therefore, its convergence radius r=1 =2.

Again, lim(n )un+1 un丨=丨x丨 r<1, 丨x丨 r=2, and its convergence interval is |x|<2。

Let s(x) = [x (n+1)] [(n+1)2 n]. In its convergence interval, the derivative of s(x) is for x, and there is s'(x)=∑(x^n)/2^n=∑(x/2)^n=1/(1-x/2)=2/(2-x)。

Both sides are integrated from 0 to x, s(x) = (0,x)s'(x)dx=∫(0,x)2dx/(2-x)=-2ln(2-x)。

FYI.

First find r, get r=2, when x=plus or minus 2, the addition term does not tend to 0, divergence. Then we know that the convergence interval is [-2,2]. Then find the product and derivative method to find the function.

Intelligence questions, IQ test. How many squares are there?

16 + 9 + 4 + 5 + 5 + 1 = 40 (pcs).

Quiz everyone: This is a math problem that can measure whether a person has business acumen. Master Wang is selling fish, a pound of fish at a price of 45 yuan, now a big sale at a loss, the customer bought a kilogram for 35 yuan, gave Master Wang 100 yuan fake money, Master Wang has no change, so he asked a neighbor for 100 yuan.

Afterwards, the neighbor found out that the money was fake in the process of depositing money, and it was confiscated by the bank, and Master Wang lost 100 yuan to the neighbor, how much did Master Wang lose in total?

Note: The difference between catties and kilograms.

A total loss of 100 + (45 2-35) = 100 + 55 = 155 yuan.

4. You can set the proportional coefficient of separation, and the coefficient will be eliminated when it is finally converted to the equation.