Anya x Damian
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Anya x Damian
Hôm qua lúc 21:36

cần gấp ạ mai minh nộp bài

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Anya x Damian
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Sinh Viên NEU
23 giờ trước (2:33)

E bổ sung đề nhé

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Tiến
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a: Xét ΔAHB vuông tại H và ΔAHC vuông tại H có

AB=AC

AH chung

Do đó: ΔAHB=ΔAHC

b: Ta có:ΔAHB=ΔAHC

=>\(\widehat{HAB}=\widehat{HAC}\)

mà \(\widehat{HAC}=\widehat{NHA}\)(hai góc so le trong, NH//AC)

nên \(\widehat{NHA}=\widehat{NAH}\)

=>NA=NH

Ta có: \(\widehat{NHA}+\widehat{NHB}=\widehat{AHB}=90^0\)

\(\widehat{NAH}+\widehat{NBH}=90^0\)

mà \(\widehat{NHA}=\widehat{NAH}\)

nên \(\widehat{NHB}=\widehat{NBH}\)

=>NH=NB

mà NA=NH

nên NA=NB

=>N là trung điểm của AB

ΔABH=ΔACH

=>BH=CH

=>H là trung điểm của BC

Xét ΔABC có

BM,AH là các đường trung tuyến

BM cắt AH tại E 

Do đó: E là trọng tâm của ΔABC

Xét ΔABC có

E là trọng tâm

CN là đường trung tuyến

Do đó: C,E,N thẳng hàng

c: Xét tứ giác AHBK có

N là trung điểm chung của AB và KH

nên AHBK là hình bình hành

=>AK//BH và AK=BH

ta có: AK=BH

BH=CH

Do đó: AK=CH

ta có: AK//BH

H\(\in\)BC

Do đó:AK//HC

Xét tứ giác AKHC có

AK//HC

AK=HC

Do đó: AKHC là hình bình hành

=>AH cắt KC tại trung điểm của mỗi đường

mà I là trung điểm của KC

nên I là trung điểm của AH

=>I nằm trên AH

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a) Vì tam giác ABC cân tại A nên AB = AC. 
$-$ AH là đường cao của tam giác ABC nên AH ⊥ BC và AH = AH. 
$\Rightarrow$ Do đó, ta có ΔAHB = ΔAHC (theo định lý cạnh góc cạnh).
b) Vì BM là đường trung tuyến của ΔABC nên ME = 1/2 MH. 
$-$ Vì NH // AC và M là trung điểm của BC nên MN = 1/2 MH = ME. 
$-$ Do đó, E là trung điểm của đoạn thẳng MN. 
$\Rightarrow$ Theo định lý về đường trung tuyến trong tam giác, ta có N, E, C thẳng hàng.
c) Vì NH = NK và I là trung điểm của KC nên HI = IK. 
$-$ Do đó, I là trung điểm của HK. 
$\Rightarrow$ Vì H, I, A thẳng hàng nên I nằm trên AH.

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a: Sửa đề: ΔBHC=ΔCKB

Xét ΔKBC vuông tại K và ΔHCB vuông tại H có

BC chung

\(\widehat{KBC}=\widehat{HCB}\)

Do đó: ΔKBC=ΔHCB

b: Ta có: ΔKBC=ΔHCB

=>\(\widehat{KCB}=\widehat{HBC}\)

=>\(\widehat{EBC}=\widehat{ECB}\)

=>ΔEBC cân tại E

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Anya x Damian
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a) Tam giác ABC vuông tại A nên tổng số đo các góc trong tam giác là 180 độ. 
$\Rightarrow$ Do đó, góc ABC = 180 độ - 90 độ - 52 độ = 38 độ.
b) Ta có:
$-$ AB = CD (do cùng vuông góc với AC)
$-$ AM = CM (do M là trung điểm của AC)
$-$ ∠BAM = ∠DCM (do cùng bằng 90 độ)
$\Rightarrow$ Do đó, △ABM = △CDM (theo nguyên lý tam giác cân).
c) Ta có:
$-$ ∠ADC = ∠ABC (do cùng vuông góc với AC)
$-$ ∠DAC = ∠BAC (do cùng bằng 90 độ)
$\Rightarrow$ Do đó, AD // BC (theo định lý hai góc cùng chỗ).
d) Ta có:
$-$ IM = KM (do I, K là trung điểm của AB và CD)
$-$ ∠IMK = 180 độ (do IM // BC và BC // KM)
$\Rightarrow$ Do đó, ba điểm I, M, K thẳng hàng.

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Nguyễn Đình Sex
Xem chi tiết
A DUY
Hôm qua lúc 20:59

Gọi số cây ba lớp 7A, 7B, 7C trồng được lần lượt là x, y, z, vì chúng tỉ lệ lần luợt với 9, 8, 7 nên x/9= y/8= z/7.

Vì số cây trồng được của lớp 7C ít hơn số cây trồng được của lớp 7A là 10 cây nên x- z= 10

Ta có: x/9= y/8= z/7 và x-z= 10

Theo t/c dãy tỉ số bằng nhau, ta có:

x/9= y/8= z/7= x-z/9-7= 10/2= 5

Vì x/9= 5 nên x= 5.9= 45

    y/8= 5 nên y= 5.8= 40

    z/7= 5 nên z= 5.7= 35

Vậy lớp 7A trồng được 45 cây, lớp 7B trồng được 40 cây và lớp 7C trồng được 35 cây.

chúc bạn học tốt!

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longk11
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Sửa đề: giao điểm của CN với BD là Q

Xét tứ giác ABCD có

AB//CD

AD//BC

Do đó: ABCD là hình bình hành

=>AC cắt BD tại trung điểm của mỗi đường

=>O là trung điểm chung của AC và BD

Xét ΔABC có

BO,AM là các đường trung tuyến

BO cắt AM tại P

Do đó: P là trọng tâm của ΔABC

=>\(BP=\dfrac{2}{3}BO=\dfrac{2}{3}\cdot\dfrac{1}{2}\cdot BD=\dfrac{1}{3}BD\)

Xét ΔDAC có

CN,DO là các đường trung tuyến

CN cắt DO tại Q

Do đó: Q là trọng tâm của ΔDAC

=>\(DQ=\dfrac{2}{3}DO=\dfrac{2}{3}\cdot\dfrac{1}{2}\cdot DB=\dfrac{1}{3}DB\)

ta có: BP+PQ+QD=BD

=>\(PQ+\dfrac{1}{3}BD+\dfrac{1}{3}BD=BD\)

=>\(PQ=\dfrac{1}{3}BD\)

=>BP=PQ=QD

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Anya x Damian
Xem chi tiết

a: Xét ΔMAC và ΔMEB có

MA=ME

\(\widehat{AMC}=\widehat{EMB}\)(hai góc đối đỉnh)

MC=MB

Do đó: ΔMAC=ΔMEB

=>AC=EB

Ta có: ΔMAC=ΔMEB

=>\(\widehat{MAC}=\widehat{MEB}\)

mà hai góc này là hai góc ở vị trí so le trong

nên AC//BE

 

b: ta có: AC//BE

MP\(\perp\)AC

Do đó: MP\(\perp\)BE

=>MQ\(\perp\)BE

Xét ΔMQE vuông tại Q và ΔMPA vuông tại P có

ME=MA

\(\widehat{MEQ}=\widehat{MAP}\)(cmt)

Do đó: ΔMQE=ΔMPA

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Minh Tuấn
Hôm qua lúc 21:06

 

 

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Lò Nguyễn Minh Đức
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Khinh Yên
Hôm qua lúc 21:15

X. Read the passage, and choose the correct answer A, B, C or D for each question.

        Almost all our energy comes from oil, coal, and natural gas. We call them fossil fuels. The earth’s fossil fuels are running out. What will happen when there is no oil, coal and gas on the earth?

        Scientists are trying to find and use other alternative sources of energy. We can use energy from the sun, the wind, and the water.

        Solar energy is unlimited. The sun supplies all the energy used to grow plants, to evaporate water for rain, and to maintain the temperate of the planet. All are necessary for human life. If we are able to collect solar energy, we will be sure to have this abundant source od power.

        1.        From which do plants on the earth get energy?        

        A. stars        B. the Mars        C. the moon        D. the sun

        2.        What are the other words or phrase for fossil fuels?        

        A. natural gas        B. oil        C. coal        D. oil, gas, natural gas

        3.        Natural sources of energy are energy from                 .

        A. wind        B. the sun        C. water        D. the sun, wind, water

        4.        The word “abundant” in the passage is closet in meaning with                 .

        A. plentiful        B. limited        C. natural        D. necessary

        5.        We are asking the question, “What will happen when there is no oil, coal, and gas on the earth?” because                 .

        A. we are now depending so much on oil, coal, and natural gas        

        B. other sources of energy can come from the sun, wind, and water

        C. we are looking forward to seeing great changes

        D. we are looking for other alternative sources of energy

XI. Read the passage and write T (True) or F (False) next to the sentences.        

Solar energy

Solar energy is the energy that we get from the sun and converted into thermal or electrical energy. Solar energy is a renewable energy because it will never end as long as the sun remains. Solar energy is also pollution-free because there will be no pollution occurring while producing solar energy. Solar energy is not only pollution-free energy but also its maintenance cost is very low, so to maintain a solar power plant, less manpower is required than others. Also, one can get a non-stop power supply even in the rainy season with the help of solar panels. However, there are also some disadvantages of using solar energy like the initial setup cost of panels and battery is very high. To store the solar energy in a large number, one needs a personal room for the batteries. It pollutes the environment chemically.

1. Solar energy is the energy that we get from the sun.                               ____T____

2. Solar energy is renewable and pollution-free energy.                 ___T_____

3. Solar energy will end one day.                 _____F___

4. Maintaining a solar power plant requires a lot of manpower                ____F____

5. One can get a non-stop power supply even in the rainy season with the help of solar panel____T___

6. One of the disadvantages of using solar energy is the very high initial setup cost.                 ____T____

5.                       Read the following passage, and then tick the correct answers: true (T), or false (F).

        “ My name is Professor Roberts, and tonight, I’m going to tell you how to save energy in your homes. Most of us use too much energy. You can reduce this amount by: using low energy light bulbs, using solar energy, turning off unnecessary lights, preparing food before turning on the cooker. If you follow these simple rules, you will not only save energy but also keep the environment cleaner.”

        

1. The professor tells us about the ways to cut down on wastes of energy in our offices.        F

2.        Almost everyone consumes too much energy.        T

3.        Although solar energy is clean, the lecturer doesn’t advise us to use it.        F

4.        The speaker gives four simple rules.        T

5.         According to the speaker, energy will be saved.        T

XIII. Read the text and choose the correct answer (A, B, C or D) for each space.

        Most of our energy comes from fossil fuels (1) _______ coal, oil, and natural gas. Although the supplies of these energy sources are plentiful, they are limited. The (2) _______ of coal and oil is also having very harmful impacts (3) _______ the environment. However, fossil fuels are not the only source of energy and burning fuel is not the only way to (4) _______ heat and motion. Renewable energy offers us a better way. Some energy sources are renewable because they are naturally available (5) _______ last forever. Some sources have enormous supply so human can never use them up. Moreover, renewable energy sources (6) _______ much smaller impacts on the environment than fossil and nuclear fuels. (7) _______ include solar energy, which comes from the sun and can be converted into electricity and heat. Wind, geothermal energy from inside the earth, biomass from plants, and hydropower from water are (8) _______ renewable sources of energy.

1.         A. include        B. such as        C. unlike                D. is

2.         A. burn        B. to burn        C. burns                D. burning

3.         A. at        B. of                C. on                D. in

4.         A. produce        B. save        C. reuse                D. recycle

5.         A. so        B. but                C. for                D. and

6.         A. are        B. had        C. have                D. has

7.         A. It        B. There        C. That                D. They

8.         A. also        B. only        C. last                D. then

XIV. Rearrange the words or phrases to make meaningful sentences.        

1. our energy/ come/ oil, / from / and natural gas / Most of / gas/

        🡲         Most of our energy come from oil, gas and natural gas.

2. renewable / Wind/ sources/ and / are / water

        🡲         Wind and water are renewable  sources

3. are/ We/ looking for/ sources of energy/ cheap, / clean/ and effective

        🡲         We are looking for cheap, clean and effective sources of energy

4. will/ We/ solar energy/use/ solve/ to/ the problem/ of energy shortage

        🡲         We will use solar energy to solve the problem of energy shortage

5. hydro energy / The / is / teacher / right now / teaching / about/ us/.

        🡲         The teacher is teaching us about hydro energy right now

6. use / Do / you / in / energy / your house? / solar

        🡲         Do you use solar energy in your house?

7. going out / We / turn off / always / the lights / before /.

        🡲         We always turn off the lights before going out

8. electricity. / John / to/ uses / low energy / save / light bulbs /

        🡲         John uses low energy light bulbs to save electricity

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Sinh Viên NEU
Hôm qua lúc 0:53

X. Read the passage, and choose the correct answer A, B, C or D for each question.

        Almost all our energy comes from oil, coal, and natural gas. We call them fossil fuels. The earth’s fossil fuels are running out. What will happen when there is no oil, coal and gas on the earth?

        Scientists are trying to find and use other alternative sources of energy. We can use energy from the sun, the wind, and the water.

        Solar energy is unlimited. The sun supplies all the energy used to grow plants, to evaporate water for rain, and to maintain the temperate of the planet. All are necessary for human life. If we are able to collect solar energy, we will be sure to have this abundant source od power.

        1.        From which do plants on the earth get energy?        

        A. stars        B. the Mars        C. the moon        D. the sun

        2.        What are the other words or phrase for fossil fuels?        

        A. natural gas        B. oil        C. coal        D. oil, gas, natural gas

        3.        Natural sources of energy are energy from                 .

        A. wind        B. the sun        C. water        D. the sun, wind, water

        4.        The word “abundant” in the passage is closet in meaning with                 .

        A. plentiful        B. limited        C. natural        D. necessary

        5.        We are asking the question, “What will happen when there is no oil, coal, and gas on the earth?” because                 .

        A. we are now depending so much on oil, coal, and natural gas        

        B. other sources of energy can come from the sun, wind, and water

        C. we are looking forward to seeing great changes

        D. we are looking for other alternative sources of energy

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Sinh Viên NEU
Hôm qua lúc 0:55

XI. Read the passage and write T (True) or F (False) next to the sentences.        

Solar energy

Solar energy is the energy that we get from the sun and converted into thermal or electrical energy. Solar energy is a renewable energy because it will never end as long as the sun remains. Solar energy is also pollution-free because there will be no pollution occurring while producing solar energy. Solar energy is not only pollution-free energy but also its maintenance cost is very low, so to maintain a solar power plant, less manpower is required than others. Also, one can get a non-stop power supply even in the rainy season with the help of solar panels. However, there are also some disadvantages of using solar energy like the initial setup cost of panels and battery is very high. To store the solar energy in a large number, one needs a personal room for the batteries. It pollutes the environment chemically.

1. Solar energy is the energy that we get from the sun.                               ____T____

2. Solar energy is renewable and pollution-free energy.                 ___T_____

3. Solar energy will end one day.                 ____F____

4. Maintaining a solar power plant requires a lot of manpower                ____F____

5. One can get a non-stop power supply even in the rainy season with the help of solar panel____T___

6. One of the disadvantages of using solar energy is the very high initial setup cost.                 ___T_____

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