In the field, the sun comes out For example: on the sea, the sun jumps out. On the grassland, the sun comes out. In the forest, the sun is sung by the birds. In the mountain village, the sun comes out. In the city, the sun comes out. In the field, the sun comes out.

In the field, the sun comes out For example: on the sea, the sun jumps out. On the grassland, the sun comes out. In the forest, the sun is sung by the birds. In the mountain village, the sun comes out. In the city, the sun comes out. In the field, the sun comes out.

In the city, the sun comes out (by bus)
In the field, the sun comes out (holding the grass)

The whole is as follows: a pleasure boat paddles gently in the air
A strong wind pattered across the lake
A pony was whistling across the valley
A small stream was clattering along the road

A pleasure boat paddled gently across the lake
A strong wind whirred through the air
A colt pattered along the road
A small stream was clattering through the valley

How to solve this problem!

X & # 178; - half X - third = 0
6x²-3x-2=0
x=(3±√57)/12
x=1/4±1/12√57

It is known that the gas density in a bubble is 1.29kg/m3, and the average molar mass is 0.029kg/mol. The Avogadro constant Na is 6.02 × 1023mol-1, and the average diameter of the gas molecule is 2 × 10-10m. If the gas in the bubble can completely turn into liquid, please estimate the ratio of the liquid volume to the original gas volume

Let v 1 be the volume of gas, V 2 be the volume of liquid, M = ρ v 1, n = mmna, V 0 = 43 π (D 2) 3 = 16 π D 3, V 2 = n V 0, V 2V 1 = π ρ, n ad36m = 3.14 × 1.29 × 6 × 1023 × (2 × 10 −)

Define a new operation x * y = x-2xy + 3Y, try to calculate 2A * B - (- 2A) * (- 3b)

x*y=x-2xy+3y,
2a*b-(-2a)*(-3b)
=2(a-2ab+3b)-(-2a-12ab-9b)
=2a-4ab+6b+2a+12ab+9b
=4a+8ab+15b

If the filament of a bulb is broken, why will the resistance of the filament decrease when the filament is put on again
If you don't use Ohm's law, what's the answer?

Because the resistance is affected by the cross-sectional area and length of the resistance itself
The resistance is proportional to its length, that is, the longer the resistance is, the greater the resistance is
The resistance is inversely proportional to its cross-sectional area
In this problem, the overall length is small, and the cross-sectional area is large at the breaking point, so the resistance is small

If (x-3) &# 178; = 169, (Y-1) &# 179; = - 0.125,
Find the value of √ (x) - √ (2XY) - & # 179; √ (16y-x)
Is this question two cases, one result, and finally equal to two?

Not two
x-3=±13
X = - 10 or x = 16
If the root x is meaningful, then x = 16
y-1=-0.5
y=1/2
So the original formula = √ 16 - √ 16 - & # 179; √ (8-16)
=4-4-(-2)
=2

20 simple score calculation questions for me

1.3/7 × 49/9 - 4/3
2.8/9 × 15/36 + 1/27
3.12× 5/6 – 2/9 ×3
4.8× 5/4 + 1/4
5.6÷ 3/8 – 3/8 ÷6
6.4/7 × 5/9 + 3/7 × 5/9
7.5/2 -（ 3/2 + 4/5 ）
8.7/8 + （ 1/8 + 1/9 ）
9.9 × 5/6 + 5/6
10.3/4 × 8/9 - 1/3
11.7 × 5/49 + 3/14
12.6 ×（ 1/2 + 2/3 ）
13.8 × 4/5 + 8 × 11/5
14.31 × 5/6 – 5/6
15.9/7 - （ 2/7 – 10/21 ）
16.5/9 × 18 – 14 × 2/7
17.4/5 × 25/16 + 2/3 × 3/4
18.14 × 8/7 – 5/6 × 12/15
19.17/32 – 3/4 × 9/24
20.3 × 2/9 + 1/3
21.5/7 × 3/25 + 3/7
22.3/14 ×× 2/3 + 1/6
23.1/5 × 2/3 + 5/6
24.9/22 + 1/11 ÷ 1/2
25.5/3 × 11/5 + 4/3
26.45 × 2/3 + 1/3 × 15
27.7/19 + 12/19 × 5/6
28.1/4 + 3/4 ÷ 2/3
29.8/7 × 21/16 + 1/2
30.101 × 1/5 – 1/5 × 21
1. Mental arithmetic
(1)58+42= (2)87－45= (3)125×8=
(4)50×12= (5)804÷4= (6)134＋66=
(7)1000－98= (8)720÷5= (9)0÷47=
2. First fill in the operation order of the following questions, and then calculate the number
(1)168+36－36+32=
(2)153－5×14+83=
(3)50×5÷50×5=
3. Judgment: mark "√" for right and "×" for wrong
(1) 13 × 15 and 15 × 13 have the same meaning
(2) The calculation result of 3000 ／ 425 ／ 8 must be less than that of 3000 ／ (425 × 8). ()
(3) The product of two factors is 800. If one factor is constant and the other factor is reduced by 20 times, then the product is 40
(4) Formula: "750 △ 25 + 35 × 2" means the quotient of 750 divided by 25; plus 2 times of 35, what is the sum
(5)24×25=6×4×25=6+100=106( )
4. Simple calculation method
(1)3786－499
(2)32×25×125
(3)1653－338－662
(4)7987+350+2013+450
(5)38×38+62×38
(6)452+99×452
(7)201×79
(8)50×125×4×8
5. Calculate the following questions:
(1)340×(120－40÷8)
(2)45×(720－1957÷19)
(3)86+[4500+(2088÷36)÷2]
(4)396×[74－(4875÷15－13×21)]
(5)[1054－(174－168)]÷8
(6)6048÷[(107－99)×9]
6. Use the comprehensive formula
(1) What is the quotient of 42 minus 28 divided by 14?
(2) What's the sum of 840 minus 480 divided by 240, plus 162?
(3) 258 plus the sum of 42 times 185 minus 158, what's the product?
(4) 1080 minus the product of 6 and 12, and then divided by 12, what's the quotient?
(5) Subtract the product of 60 and 80 from 6000, and divide the difference by 120. What's the quotient?
(6) How much more is the product of 12, 18 and 20 than their sum?
The calculation is simple
408－12×24 （46＋28）×60 42×50－1715÷5
32＋105÷5 （108＋47）×52 420×（327－238）
(4121+2389)÷7 671×15-974 469×12+1492
405×(3213-3189) 5000-56×23 125×(97-81)
6942+480÷3 304×32-154 20+80÷4-20＝
100÷（32-30）×0＝ 25×4-12×5＝
70×〔（42-42）÷18〕＝ 75×65+75×35＝
Calculate the following questions in a simple way
1、89+124+11+26+48 2、875-147-23
3．25×125×40×8 4、147×8+8×53
5、125×64 6、0.9＋1.08＋0.92＋0.1
Calculation by simple method
①89+124+11+26+48 ②875-147-23
③147×8+8×53 ④125×64
Calculate the following questions
1．280＋840÷24×5 2．85×(95－1440÷24)
3．58870÷(105＋20×2) 4．80400－(4300＋870÷15)
5．1437×27＋27×563 6．81432÷(13×52＋78)
7．125×(33－1) 8．37.4－(8.6＋7.24－6.6)
Calculation. (1 ∶ 1)
（1）156×107-7729 （2）37.85-（7.85+6.4）
（3）287×5+96990÷318 （4）1554÷[（72-58）×3]
Out of form calculation
2800÷ 100＋789 （947－599）＋76×64
1．36×(913－276÷23) 2．(93＋25×21)×9
3．507÷13×63＋498 4．723－(521＋504)÷25
5．384÷12＋23×371 6．(39－21)×(396÷6)
（1）156×[(17.7-7.2)÷3] （2）[37.85-（7.85+6.4）] ×30
（3）28×(5+969.9÷318) （4）81÷[（72-54）×9]
57×12－560÷35 848－640÷16×12
960÷（1500－32×45） [192－（54＋38）]×67
138×25×4 (13×125)×(3×8) (12+24+80)×50 704×25 25×32×125 32×(25+125)
178×101－178 84×36+64×84 75×99+2×75 83×102－83×2 98×199
123×18－123×3+85×123 50×(34×4)×3 25×（24+16） 178×99+178
79×42+79+79×57 7300÷25÷4 8100÷4÷75 75×27+19×2 5 31×870+13×310
4×(25×65+25×28) 138×25×4 (13×125)×(3×8) (12+24+80)×50
25×32×125 32×(25+125) 102×76 58×98
178×101－178 84×36+64×84 75×99+2×75 83×102－83×2
98×199 123×18－123×3+85×123 50×(34×4)×3 25×（24+16）
178×99+178 79×42+79+79×57 7300÷25÷4 8100÷4÷75
2/1+3/1
6/5+9/3

If the line L passes through the left focus of the hyperbola x ^ 2 / 4-y ^ 2 / 2 = 1 and has only one common point with the hyperbola, the equation of the line L is obtained

A ^ 2 = 4, B ^ 2 = 2, C ^ 2 = 6, left focus f (- √ 6,0)
Let L: y = K (x + √ 6)
Simultaneous with elliptic equation: (1-2k & sup2;) x & sup2; - 4 √ 6K & sup2; x-12k & sup2; - 4 = 0
When 1-2k & sup2; = 0, there is only one intersection, and K = ± √ 2 / 2
Or when two intersection points coincide, it can also be regarded as a focus. In this case, (1-2k & sup2;) x & sup2; - 4 √ 6K & sup2; x-12k & sup2; - 4 = 0 is a quadratic equation with one variable, and the two roots are equal, so there is no solution
The equation of L: y = ± √ 2 / 2 (x + √ 6)

10 light emitting diodes in series (voltage 3.2-3.4v, current 20mA) connected to 220 V AC, what resistance value is required
How much resistance is needed to connect only one? If 20 are connected, how much resistance is needed?

1. 10 light-emitting diodes with a voltage of 3.2-3.4v are connected in series. The total voltage is 32-34v, and the intermediate value is 33V. Then the terminal voltage of the step-down resistor is 220-33 = 187 (V). 2. The current of the light-emitting diode is 20mA, and the current flowing through the resistor is 20mA, so the resistance value should be 187 (V) × 20mA