7a-3b+5c=11
3a+2b-7c=(-3)
2a-5b+2c=(-20)
tìm abc
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\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\3+x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-3\end{matrix}\right.\)
III. Choose the best answer to complete each of the following sentences.
1. She __________ from England.
A. come B.comes C. don’t come D. goes
2. __________ She __________ French?
A. Do / speaks B. Does / speaks C. Is / speak D. Does / speak
3. She __________ from America.
A. doesn’t come B. don’t comes C. doesn’t comes D. does comes
4. I __________ a bath now. Wait mea minute.
A. have B. am have C. am having D. is having
5. He__________ a glass of lemonade before breakfast.
A. is B. have C. has D. does
6. __________ he __________ three children?
A. Do / have B. Does / has C. Does / have D. Is / have
7. He __________ television at the moment.
A. watch B. watches C. is watching D. is watch
8. __________ Huong 10 years old?
A. are B. is C. do D. does
9. My classmates __________ on picnic every month.
A. went B. goes C. going D. go
10. " __________ do you travel to school?" ____ "By bus."
A. How B. What C. Why D. Where
11. I __________ know the correct answer.
A. am not B. not C. don’t D. doesn’t
12. We enjoy our summer camping _________ foreign friends.
A. with B. of C. in D. at
13. _________the spring, I always ride my bike
A. On B. At C. In D. For
14. What _________Ba often do on Sundays? He plays soccer.
A. is B. does C. do D. would
15. 7. He doesn’t have _________ money.
A. a B.an C. some D. any
19. “_________ books are they?” ___ They’re mine.
A. What B. Who C. Whose D. Which
20. Don’t buy _________bread at the shop. There’s a lot of in the kitchen.
A. any B. some C. a D. many
Ta thấy trong 3 số thì số b là nhỏ nhất
b kém a 10 lần
b kém c 100 lần
Tổng a + b + c = 100b + b + 10b = 111b = 221,778
Suy ra b = 1,998
Do đó số a là 19,98; số c là: 199,8
Vậy số thập phân a cần tìm là 19,98.
Diện tích xung quanh là:
\(\left(25+12\right)\cdot2\cdot2,5=5\cdot37=185\left(m^2\right)\)
Diện tích cần lát gạch là:
\(185+25\cdot12=185+300=485\left(m^2\right)\)=4850000(cm2)
Diện tích 1 viên gạch là 502=2500(cm2)
Số viên gạch cần dùng là:
4850000:2500=1940(viên)
=>Chọn D
1 bỏ for
2 more lazier => lazier
3 kind => kinds
4 interested => interesting
5 very => much
a = 2; b = 6; c = 3
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