People's education press seventh grade mathematics world pass 11 pages 17 questions

People's education press seventh grade mathematics world pass 11 pages 17 questions

What is the world's best

80:2 = 30:45 = 2.5:0.5 = 1 / 10 = 1 / 8 = 0.3:0.9 = 0.4:0.5 = 13:39 = 46:23 = 1 / 4:8 = 1 / 8=
15:12= 0.7:4.9= 0.8：1.6=

80:2 = 40:1 30:45 = 1:2:3 2.5:0.5 = 5:1 10:1 = 8:1 = 4:50.3:0.9 = 1:30.4:0.5 = 4:5 13:39 = 1:3 46:23 = 2:1 4:8:1 = 2:1 15:12 = 5:40.7:4.9 = 1:70.8:1.6 = 1:2
It's over!

Let Sn be the sum of the first n terms of the arithmetic sequence an, if a20120, then the minimum positive integer value n of Sn > 0 is
A 2013 B 2014 C 4023 D 4024

a20120zuix
Then a1 + a4023 = 2a20120
So the minimum n is 4024

The living room of the mischievous family is 3 meters long and 2.5 meters wide. How many centimeters of square tiles can be chosen to finish the paving, and the number of tiles is the least
…… How much is the minimum?

As an interior designer, I suggest that you buy 600 * 600mm floor tiles to pave, because there are five vertical tiles, which are a little more than 4 fast. After 23 tiles are paved, 3 * 2.5 = 7.5 / 0.36 = 21 tiles, which is at least 21 tiles with loss in theory

Uncle Zhang bought a house worth 560000 yuan
Uncle Zhang bought a house with a value of 560000 yuan, paid 260000 yuan and 300000 yuan, and planned to pay it off in 10 years. According to China's loan interest rate, the annual interest rate of housing provident fund loan with a term of more than five years is 4.5%. When Uncle Zhang paid off the loan, how much did he pay for the house?

If you buy it with provident fund, the interest of 300000 yuan after 10 years of loan is 73104 yuan

Calculation of 1-sin ^ 2acos ^ 2 β + cos ^ 2 α sin ^ 2 β

1-sin ^ 2acos ^ 2 β + cos ^ 2 α sin ^ 2 β = 1 + cos ^ 2 α sin ^ 2 β - Sin ^ 2acos ^ 2 β = 1 + (COS a * sin β) ^ 2 - (sin a * cos β) ^ 2 = 1 + (COS a * sin β + sin a * cos β) (COS a * sin β - sin a * cos β) = 1 + sin (a + β) * sin (β - a)

In the handicraft class, Mr. Tang asked the students to cut off an isosceles right triangle at one corner of a rectangle. What's the area of the remaining part?
The width of the rectangle is 14cm, the length is 17cm, the width minus one right angle side of the triangle is 9cm. Please!

S=14×17-9×9÷2
=238-40.5
=197.5 square centimeters

Formula of resistance law of series circuit

Total resistance R = R1 + R2 + R3 +
The total resistance of a series circuit is equal to the sum of the resistances

Prove the inequality: 1 ≤∫ (0,1) √ 1 + X ∧ 4 DX ≤ 4 / 3

The expression under the integral sign is greater than or equal to 1, which can be proved on the left after integration. The expression under the root sign is less than or equal to (1 + 2x ^ 2 + x ^ 4), which is 1 + x ^ 2, which can be proved on the right side of this integral

The formula for calculating the area of a square is expressed in letters______ ．

The formula for calculating the area of a square is expressed in letters: S = A2. So the answer is: S = A2