It's 1 / 2 1 / 3 1 / 10 1 / 15 1 / 26 1 / 35? Through what kind of observation can we get the answer? How to start with such questions? The tenth is right. I'm sorry

It's 1 / 2 1 / 3 1 / 10 1 / 15 1 / 26 1 / 35? Through what kind of observation can we get the answer? How to start with such questions? The tenth is right. I'm sorry

Pay attention to the denominator. Is it close to the square
2=1^2+1
3=2^2-1
10=3^2+1
15=4^2-1
26=5^2+1
35=6^2-1
The denominator of the nth term is n ^ 2 + (- 1) ^ (n + 1)
So the general formula is 1 / [n ^ 2 + (- 1) ^ (n + 1)]

The diameter of the flywheel is 1.2m, rotate counter clockwise at the speed of 300r / min, and calculate 1) the number of radians that the flywheel rotates every 1s, 2) the arc length that a point on the axle rotates every 1s?
To cut a sector plate on a circular metal plate with radius OA = 100cm and make its arc AB length 112cm, what is the central angle AOB?

1 300 R / min is 300 R / 60 s, that is, 5 turns in 1 s, the radian is 2 pies, 5 turns is 10 pies, 2 1 s, 5 turns is 5 * 360 = 1800 degrees, the arc length of a point on the axle every 1 s = n / 180 * 3.14 * r = 1800 / 180 * 3.14 * 0.6 = 6 pies, 3 arc length AB = n / 180 * 3.14 * r = 112, that is, n = 64.2

A + A / 1 = root 10, find the value of A-A / 1
If you can surf the Internet frequently, give me Q,
ha-ha

A + A / 1 = root 10, find the value of A-A / 1
(a+1/a)^=a^+1/a^+2 =10 a^+1/a^=8
(a-1/a)^=a^+1/a^-2=6
A-1 / a = + radical 6 - radical 6

The formula of profit and loss problem
To be more specific, there should be examples

One profit and one loss (common formula): (profit plus loss) divided by (difference of two distributions) other (Advanced): the critical point of profit and loss is the base point of stock trading volume of an exchange. If it exceeds this point, profits will be realized, otherwise losses will be realized. The basic model for calculating the critical point of profit and loss is set as P representing profits, V representing sales volume, SP representing unit price, VC representing

Bond price calculation formula and interest rate problem
A 2-year bond, with a face value of 1000 yuan, a coupon rate of 10%, interest paid once a half year, and a market price of 600 yuan, yields r.21000 * 10% 1000
Formula 1: 600 = ∑--+——————
T = 2 (1 + R) ^ 4 (1 + R) ^ 2 this is the bond formula in one book. But I saw a different calculation method in another book
50 50 50 50 1000
Formula 2: 600 = -- + -- + -- + -- + -- + -- + -- + -- + -- + --————
1+r/2 （1+r/2）^2 (1+r/2)^3 (1+r/2)^4 （1+r/2）^4
The two formulas are different. Is formula 2 correct? I can't solve the equation to see if the two R's are the same
If the annual interest rate was 10%, which of the following would you choose?
1. 100 yuan now
2. 12 yuan at the end of each year for the next 10 years
3. 10 yuan at the end of each year, and this situation lasts forever
4. 200 yuan at the end of the seventh year
5. Now it's 50 yuan, and the annual payment is decreasing at a rate of 50% and it continues
6. Now it's 5 yuan, and the annual payment is growing at 5% and continues
Formula correction 2 1000 * 10% 1000
Formula correction: formula 1:600 = ∑--+——————
t=2 (1+r)^4 （1+r)^2

Coupon yield, also known as face value yield, refers to the ratio of interest income to face value, which is numerically equivalent to the face interest rate. Obviously, the face yield assumes that the purchase value of the bond is equal to face value, and does not consider other sources of income, so the face yield can only be the simplest measure of yield, It doesn't account for the investment value of bonds

To find the formula of mathematical profit and loss problem,

Profit = price - purchase price
Price = original price times discount
Profit: Price > purchase price
Loss: price < purchase price

A formula for solving profit and loss problems
It's better to write in the addition and subtraction

One profit and one loss (common formula): (profit plus loss) divided by (difference between two distributions) other (Advanced): the critical point of profit and loss is the base point of stock trading volume of an exchange. If it exceeds this point, profits will be realized, otherwise losses will be realized. The basic model for calculating the critical point of profit and loss is that P represents profits, V represents sales volume, SP represents unit price, VC represents unit variable cost, FC represents fixed cost, Be stands for the critical point of profit and loss. According to the profit calculation formula, the basic model of the critical point of profit and loss can be obtained as follows: the calculation of the critical point of profit and loss can be in the form of physical object and amount: 1. Calculation by physical unit: if the unit price of a product is 10 yuan, the unit variable cost is 6 yuan, and the related fixed cost is 8 000 yuan, then the sales volume of the critical point of profit and loss (physical unit) = 8 2. Comprehensive calculation by amount: sales volume at the critical point of profit and loss (expressed by amount) = fixed cost ／ contribution gross profit rate, where contribution gross profit rate = contribution gross profit / sales income

The original price of a movie ticket is a few yuan, but now it is sold at 3 yuan. The audience will increase by half, and the income will increase by a quarter______ Yuan

The original price of a movie ticket is the original price of a movie ticket. According to the title, you can get: (x-3) x (1 + 12) (1 + 12) (1 + 14) × x, & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; the original price of a movie ticket can be: (x-3-3) (x-3) (x-3) x (1 + 12) (1 + 12) (1 + 12) (1 + 14) × x, & amp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp & nbsp; & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & & nbsp; & nbsp; &A: the original price of a movie ticket is 18 yuan

Formula of distance from point to line

Let P (x0, Y0) and the linear equation be ax + by + C = 0, then the distance from P to the straight line is d = | ax0 + by0 + C | / √ (A & # 178; + B & # 178;)
Hope to adopt

High school mathematics * has a formula about the distance between two points of a circle

(x1-x2) ^ 2 + (y1-y2) ^ 2