Add "+" or "-" in front of the numbers 3, 4, 5, 6, 7, 8 and 9 to make their sum - 10. Write as many as possible and list the formula It's three, four, five, six, seven, eight, nine

Add "+" or "-" in front of the numbers 3, 4, 5, 6, 7, 8 and 9 to make their sum - 10. Write as many as possible and list the formula It's three, four, five, six, seven, eight, nine

- 3 - 4 - 5 - 6 + 7 - 8 + 9 = -10- 3 + 4 + 5 - 6 + 7 - 8 - 9 = -10+ 3 - 4 - 5 + 6 + 7 - 8 - 9 = -10+ 3 - 4 + 5 - 6 - 7 + 8 - 9 = -10+ 3 + 4 - 5 - 6 - 7 - 8 + 9 = -10

Math score calculation (how do you think of the answer? Write more than 2 ways)
1 in 20 = (4) 1 - (5) 1
1 in 30 = (5) 1 - (6) 1
1 out of 56 = (1 out of 7) - (1 out of 8)

1 1 1
------ ＝ --- - ---
n(n+1) n n+1
As shown in the above formula, the denominator of the fraction on the left side of the equal sign must be able to be decomposed into the product of two adjacent natural numbers, and the one on the right side of the equation is the reciprocal difference of the two adjacent natural numbers

Beijing Normal University Mathematics Grade 8 Volume 2 Chapter 4 review question 18, 19 problem solving method urgent! Speed!

18. As shown in the picture, Wang Hua walks from street lamp a to street lamp B at night. When he reaches P, he finds that the top of his shadow behind him just touches the bottom of street lamp A. when he walks further 12m to reach point Q, he finds that the top of his shadow in front of him just touches the bottom of street lamp B

A two-tier bookshelf has three times as many books on the upper shelf as on the lower shelf. If 60 books on the upper shelf are moved to the lower shelf, the books on the two shelves are equal. How many books are there on the upper shelf and on the lower shelf?

There are more books in the upper layer than in the lower layer: 60 × 2 = 120 (Books); in the lower layer: 120 △ 3-1 = 60 (Books); in the upper layer: 60 × 3 = 180 (Books)

You must have experienced a strong shock in the face of the solemn and stirring scene of the flying gazelle. Please tell me your inner feelings

In order to breed, the antelope family has to sacrifice themselves for the development of the whole family. They have to let the children go first. What they are facing is that they are crushed to pieces, that there is no place to die, that is the cold cliff bottom

The riddles in Lesson 17 of the sixth grade Chinese exercise book of Jiangsu Education Press
Answers to the sixth grade Chinese exercise book of Jiangsu Education Press
Lesson 17 the answer in the valley
All answers

One question:
Awning awning awning
Urge to destroy
Enigma enigma
Two questions:
Landscape privet is intact, green and straight
Three questions:
1 5 2 6 3 4
Four questions:
Riddle: the west slope is full of pine, cypress, Zhe, privet and other miscellaneous trees, while the east slope is only full of cedar
The answer: because of the special wind direction, the snow on the east slope of the valley is always bigger than that on the west slope. When the snow is thick on the cedar to a certain extent, the elastic branches of the cedar begin to bend downward, and the snow falls from the branches, the pressure is reduced, and the branches immediately rebound, still green and straight
Enlightenment: in the face of adversity and pressure, we should not only dare to fight, but also learn to retreat appropriately, take retreat as advance, protect ourselves, so as to benefit survival and development and make final progress
Five questions:
1.C
2. Plot repeatedly, bend repeatedly, drop repeatedly, bounce repeatedly
3. Make appropriate concession under great pressure and succeed indomitably. The strong and the winner
Development exercises:
One question:
1. The three armed forces can win the commander
2. People are poor and ambition is not short
3. Be able to bend and stretch
4. Take a step back
Two questions:
You write it yourself

Solution equation: 4x-3 (20-x) = 3

Remove the brackets: 4x-60 + 3x = 3 (2 points); transfer items and merge similar items: 7x = 63 (4 points); coefficient into 1: x = 9. (6 points)

Simple calculation of 1.73 × 99 + 1.73

I'm glad to help you
1.73×99+1.73=1.73x（99+1）=1.73x100=173

Fill in the blanks in Mathematics (round)
Circle O1 and circle O2 are mutually circumscribed, and the radius ratio is 2; 3. O1m is tangent to circle O2 at point m, o2n is tangent to circle O1 at point n, and the ratio of o2n / o1m is calculated?

Because they are tangent, the two triangles are right triangles. The simplest way is to assume that the radius of circle O1 is 2 and the radius of circle O2 is 3. Then the remaining edges can be calculated according to the Pythagorean theorem, and finally the ratio is
Root 21 / 4

There is a product whose price has been reduced by 10% twice in a row. Now the selling price is 50 yuan. The original price of this product is () yuan

50/0.81