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Bài 4:
a) Xét tam giác ABM và tam giác ACM có:
AM chung.
AB = AC (Tam giác ABC cân).
BM = CM (M là trung điểm BC).
\(\Rightarrow\) Tam giác ABM = Tam giác ACM (c - c - c).
b) Xét tam giác BHM vuông tại H và tam giác CKM vuông tại K có:
\(\widehat{B}=\widehat{C}\) (Tam giác ABC cân).
\(BM=CM\) (M là trung điểm BC).
\(\Rightarrow\) Tam giác BHM = Tam giác CKM (cạnh huyền - góc nhọn).
\(\Rightarrow\) BH = CK (2 cạnh tương ứng).
a: =3/2-2/3:(4/18+3/18)
=3/2-2/3:7/18
=3/2-2/3*18/7
=3/2-12/7
=-3/14
b: =(5/8-1/5)*2-1/4
=5/4-2/5-1/4
=1-2/5=3/5
c: =(3+5/6-1/2):55/12
=10/3*12/55
=8/11
Ta có
\(a^2+1=a^2+ab+bc+ca=a\left(a+b\right)+c\left(a+b\right)=\left(a+b\right).\left(a+c\right)\\ Cmtt:b^2+1=\left(b+a\right).\left(b+c\right)\\ c^2+1=\left(c+a\right).\left(c+b\right)\)
Nên
\(\dfrac{b-c}{a^2+1}+\dfrac{c-a}{b^2+1}+\dfrac{a-b}{c^2+1}\\ =\dfrac{\left(b-c\right)}{\left(a+b\right)\left(a+c\right)}+\dfrac{\left(c-a\right)}{\left(b+c\right)\left(b+a\right)}+\dfrac{\left(a-b\right)}{\left(c+a\right)\left(c+b\right)}\\ =\dfrac{\left(b-c\right)\left(b+c\right)+\left(c-a\right)\left(c+a\right)+\left(a-b\right)\left(a+b\right)}{\left(a+b\right)\left(b+c\right)\left(c+a\right)}\\ =\dfrac{b^2-c^2+c^2-a^2+a^2-b^2}{\left(a+b\right)\left(b+c\right)\left(c+a\right)}\\ =0\)
\(\dfrac{b-c}{a^2+1}+\dfrac{c-a}{b^2+1}+\dfrac{a-b}{c^2+1}\)
\(=\dfrac{b-c}{a^2+ab+bc+ac}+\dfrac{c-a}{b^2+ab+bc+ca}+\dfrac{a-b}{c^2+ab+bc+ca}\)
\(=\dfrac{b-c}{a\left(a+b\right)+c\left(a+b\right)}+\dfrac{c-a}{b\left(a+b\right)+c\left(a+b\right)}+\dfrac{a-b}{c\left(c+a\right)+b\left(a+c\right)}\)
\(=\dfrac{b-c}{\left(a+c\right)\left(a+b\right)}+\dfrac{c-a}{\left(b+c\right)\left(a+b\right)}+\dfrac{a-b}{\left(b+c\right)\left(a+c\right)}\)
\(=\dfrac{\left(b-c\right)\left(b+c\right)+\left(c-a\right)\left(a+c\right)+\left(a-b\right)\left(a+b\right)}{\left(a+c\right)\left(a+b\right)\left(b+c\right)}\)
\(=\dfrac{b^2-c^2+c^2-a^2+a^2-b^2}{\left(a+b\right)\left(b+c\right)\left(c+a\right)}=0\)
1. bến còn lại số ô tô là:
45 - 18 + 17 = 44(chiếc)
Đáp số: 44 chiếc ô tô
REFER 1->10
Make conditional sentences:
1. Keep silent or you’ll wake the baby up. →If YOU DON'T KEEP SILENT , YOU WILL WAKE THE BABY UP……………………………………………..…..………
2. Stop talking or you won’t understand the lesson.→ If ………YOU DON'T STOP TALKING , YOU WON'T UNDERSTAND THE LESSON…………………………….....….…….
3. I don’t know her number, so I don’t ring her up.→ If I KNEW THE NUMBER, I WOULD RING HER UP…………………………………….....….……..
4. I don’t know the answer, so I can’t tell you.→ If ……I KNEW THE ANSWER, I COULD TELL YOU……………………………………….………..
5. We got lost because we didn’t have a map.→ If ……………WE HAD ……………HAD A MAP, WE WOULDN'T HAVE GOT LOST………….……..…….……
6. Susan felt sick because she ate four cream cakes. →……IF SUSAN HADN'T EATTEN FOUR FCREAM , SHE WOULDN'T HAVE FELT SICK………………………………………..……
7. Without this treatment, the patient would have died. →…IF HE HADN'T RECEIVED THIS TREATMENT, THE PATIENT WOULD HAVE DIED…………………………………….….…...
8. He lost his job because he was late every day. →……IF HE HADN'T BEEN LATE EVERYDAY, HE WOULDN'T…HAVE LOST HIS JOB………………………………………...……
9. Peter is fat because he eats so many chips. →…………IF PETER DIDN'T EAT SO MANY CHIPS,HE WOULDN'T BE FAT…………………………………………...…..
10. Robert got a bad cough because he started smoking cigarettes. →………IF ROBERT HADN'T STARTED SMOKING CIGARETTES, HE WOULDN'T HAVE GOT A BAD COUGH………………………..…..
11. She had her mother take care of her son when she went on a business trip
-> She had her son taken care of by her mother when she went on a business trip
12. I don't have enough money, so i can't buy that printer
-> If I had enough money, I'd buy a new computer.
13. Because i didn't have her number, i didn't invite her to my wedding
-> If I had had her number, I could have invited her to my wedding.
1. Keep silent or you'll wake the baby up
-> If you don't keep silent, you'll wake the baby up
2. Stop talking or you won't understand the lesson
->If you don't stop talking, you won't understand the lesson
3. I don't know her number, so i don't ring her up
->If I knew her number, I would ring her up
4. I don't know the answer, so i can't tell you
->If I knew the answer, I could tell you
5. We got lost because we didn't have a map
->If we had had a map, we wouldn't have got lost
6. Susan felt sick because she ate four cream cakes
->If Susan hadn't eaten four cream cakes, she wouldn't have felt sick
7. Without this treatment, the patient would have died
-> If it hadn't been for this treatment, the patient would have died
8. He lost his job because he was late every day
-> If he hadn't been late everyday, he wouldn't have lost his job
9. Peter is fat because he eats so many chips
-> If Peter didn't eat so many chips, he wouldn't be fat
10. Robert got a bad cough because he started smoking cigarettes
-> If Robert hadn't started smoking cigarettes, he wouldn't have got a bad cough
11. She had her mother take care of her son when she went on a business trip
-> She had her son taken care of by her mother when she went on a business trip
12. I don't have enough money, so i can't buy that printer
-> If I had enough money, I could buy that printer
13. Because i didn't have her number, i didn't invite her to my wedding
-> If I had had her number, i would have invited her to my wedding
1 I/lesson./understand/don't/this/
I don't understand this lesson
2 in/word?/Is/longest river/the nile/the/the
is the nile the longest river in the world?
3 we/get up/on/don't/sunday./early
we don't get up early on sunday
4I/ha long bay/at/arrive at/2p.m
I arrive at ha long bay at 2pm
5 those/much./bags/ cost/too
those bags cost too much
6 river/the amazon/flows/ocean./into/the atlantic
the amazon river flows into the atlantic ocean
7 play/every/the children/morning./in the park/sunday
the children play in the park every sunday morning
8 my family/in egypt./the pyramids/wants/visit/to
my family wants to visit the pyramids in egypt
1 I/lesson./understand/don't/this/
-> I don't understand this lesson.
2 in/world?/Is/longest river/the nile/the/the
-> Is the Nile the longest river in the world?
3 we/get up/on/don't/sunday./early
-> We don't get up early on Sunday.
4I/ha long bay/at/arrive in/2p.m
-> I arrive in Ha Long Bay at 2p.m.
5 those/much./bags/ cost/too
-> Those bags cost too much.
6 river/the amazon/flows/ocean./into/the atlantic
-> The Amazon river flows into the Atlantic Ocean.
7 play/every/the children/morning./in the park/sunday
-> The children play in the park every Sunday morning.
8 my family/in egypt./the pyramids/wants/visit/to
-> My family wants to visit the pyramids in Egypt.