Please help me When an engineering team is bidding, it receives the bidding documents from engineering teams a and B There are three options: 1. Team a works alone, just on schedule; 2. Team B works alone, 5 days more than the specified time limit; 3. If team a and team B cooperate for 4 days, the rest of the project will be completed by team B alone, just on schedule Q: how many days will it take for team a and team B to complete the project separately? I want to write out the complete steps,

If the construction period is x days, the work efficiency of team a is 1 / x, and that of team B is 1 / (x + 5)
According to the fact that team a and team B work together for 4 days, and the rest of the project is done by team B alone, it is just completed on schedule
4 / x + X / (x + 5) = 1. Multiply both sides by X (x + 5)
It is reduced to x = 20
A: a alone time is 20 days, B is 25 days

As shown in the figure, in square ABCD, e is the point on ad, BF bisects ∠ CBE intersects CD with F, try to explain be = CF + AE

Extend Da to point G, make Ag = CF, connect BG, in △ ABG and △ CBF, ∵ CF = Ag ∠ C ＝ bagcb = AB, ≌ ABG ≌ CBF, ≌ BFC = BGA, ∵ CBF = ABG, ∵ BF bisection, ∫ CBE intersect CD with F, ∫ CBF = EBF, ≌ ABG = EBF, ≌ ab ≌ CD, ∫ ABF = BFC, ∫ EBG

5 / 8-3 / 8, 7 / 9 + 5 / 9, 1-17 / 11, 5 / 18 + 7 / 18, 5 / 1-7, 5 / 6 + 5 / 6

5-3 of 8 = 2 of 8 = 1 of 4
7 out of 9 + 5 out of 9 = 12 out of 9 = 4 out of 3
11 out of 1-17 = 6 out of 17
5 out of 18 + 7 out of 18 = 12 out of 18 = 2 out of 3
5 out of 1-7 = 2 out of 7
5 / 6 + 5 / 6 = 10 / 6 = 5 / 3

Help to fill in the blanks in the first unit of the first volume of science test paper

1. The core of science is (), () is an important method of science learning
2. When the police solve a case, they often use () to infer the height of the criminal. The reason is that it has a certain relationship with the height of the person. When we study this relationship, we put forward questions and make hypotheses. After establishing a hypothesis, we need to design () to test the hypothesis. To test the hypothesis, we need to collect (). In the process of collecting ()
3. Scientific discovery can start from paying attention to (), exploring (), and stimulating interest at the same time, so as to enter the world of science
4. () invented the steam engine
5. The general process of scientific research is: asking questions, (), (), recording results, (), ()
6. () is the starting point of inquiry. In order to solve it, people often put forward many () and ()
7. Hypothesis and () may be correct or () must be proved
8. In scientific research, various instruments are often used to expand the scope of observation (). For example, people can see () objects with microscope, astronomical telescope can let people see () stars, and analytical balance can measure () objects' mass
9. The results of scientific discoveries need to be written and published before they can be recognized by scientists

Known: as shown in the figure, in ladder ABCD, ad is parallel to BC, angle B = 45 °, angle c = 120 ° AB = 8, then the length of CD is~

Make AE ⊥ BC at e, DF ⊥ BC at F
In RT △ Abe,
∵∠B=45º,
∴AE=AB·sin45º=4√2
∵AD‖BC
∴DF=AE=4√2
In RT △ DCF,
∵∠DCF=180º-∠BCD=60º
∴CD=DF/sin60º=(4√2)/(√3/2)=8√6/3

(3 / 4 + 2 / 3 + 1 / 6) × 1 / 12; (1-5 / 4 × 1 / 12) × 1 / 3; 1.25 × 38 + 125% × 62

(3/4+2/3+1/6)/1/12
=(9/12+8/12+2/12)*12
=19/12*12
=19
(1-4/5*1/12)/1/3
=(1-1/15)*3
=14/15*3
=14/5
1.25*38+1.25*62
=1.25(38+62)
=125
It's very simple. Think about it

Draw function images y = - 2x + 2 | x | + 3 and y = - 2x + 3|

As shown in the figure, the points m and N are on the sides BC and CD of the square ABCD respectively. It is known that the perimeter of △ MCN is equal to half of the perimeter of the square ABCD, then ∠ man=______ ．

When △ adn is rotated 90 ° clockwise around point a, we can get △ Abe,  AE = an, be = DN,  Abe =  d = 90 degree,  NAE = 90 degree and  ABC = 90 degree,  points m, B and E are collinear,  me = be + BM = DN + BM,  MCN's perimeter is equal to half of square ABCD's perimeter,  Mn + NC + MC = DC + BC = DN + NC + MC + BM,  Mn = DN + BM,  Mn = me. In △ man and △ Mae, an = aemn = meam = am,  Mn = me Therefore, the answer is 45 degrees

The 8th power of 7 × 10 is m = - cm = - mm, and the 20th power of 7.6 × 10 is m = - mm = - μ M
Come on

The eighth power of 7 × 10 m = the tenth power of 7 × 10 cm = the eleventh power of 7 × 10 mm
7.6 × 10 to the 20th Power M = 7.6 × 10 to the 23rd power mm = 7.6 × 10 to the 26th power μ M

There are 3 more than 12 pears for each child, 5 less than 6 pears for each child?

With X children
3x+12=5x-6
2x=18
x=9
There are nine children
There are 3 * 9 + 12 = 39 pears