x^2 +357=y^2(xy là số nguyên tố)
tính x và y
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1.D
2.B
3.A
4.D
5.B
6.D
7.C
8.A
9.B
10.D
11.B
12.B
13.A
14.B
15.A
16.C
17.A
18.B
19.D
20.B
1. The Great Wall of China is the world’s longer => longest structure.
A B C D
2. Traveling by tram is most => more convenient than traveling by car in this city.
A B C D
3. You must taking=> take off your shoes before entering this room.
A B C D
4. Do you think there is another mountain highest => higher than Mount Everest?
A B C D
5. Ha Long Bay is the more => most beautiful natural wonder of Viet Nam.
A B C D
6. The scenery of the Amazon rainforest in your pictures looks incredibly=> incredible.
A B C D
7. In my opinion, foreign tourists visit Hoi An just to => forits ancient houses.
A B C D
8. Missouri is longer => the longest river in the USA, but it is shorter than the Amazon.
A B C D
9. Meghalaya in India has more => the most rainy or wettest weather in the world.
A B C D
10. Lang Son is one of the coldest province => provinces in North Viet Nam.
A B C D
11. You mustn’t cheat in exams because the teacher will punish you when => if you do that.
A B C D
12. I’m so worried because I mustn’t => must be at home after school right now.
A B C D
13. It is more => the most interesting book I have ever read.
A B C D
14. What’s the better => most film you have ever seen?
A B C D
15. You mustn’t => must look after the house when your parents are away
A B C D
16. It is raining heavily outside. You shouldn't => should bring your raincoat.
A B C D
17. She always give => gives presents to her parents on Tet holiday.
A B C D
18. She will helps => help her mother decorate the house before Tet.
A B C D
19. I don't think that lucky money can bring us good => both good and bad luck.
A B C D
20. The New Year Festival in Thailand is on => inApril. It is very hot.
A B C D
a.(b - c) + c.(a - b) = b - (a - c)
a.(b - c) + c.(a - b)
= ab - ac + ac - cb
= (ab - bc) + (ac - ac)
= b.(a - c)
em xem lại đề bài nhé
`#3107.101107`
`x \div (-7) = 5^2 \div (-5)`
`\Rightarrow x \div (-7) = -5`
$\Rightarrow x = (-5) \cdot (-7)$
$\Rightarrow x = 35$
Vậy, `x = 35.`
\(\text{x:(-7) = 5^2}:\left(-5\right)\)
\(\text{x:(-7) = 25:(-5)}\)
\(\text{x:(-7) = -5}\)
\(\text{x = (-5).(-7)}\)
\(\text{x = 35}\)
\(\text{Vậy x=35}\)
thiếu dữ liệu hay s ý?
\(x^2\) + 357 = y2 ⇒ y2 > 357 mà y là số nguyên tố nên \(y\) là số lẻ
⇒ y2 là số lẻ. ⇒ y2 - 357 là số chẵn mà \(x^2\) = y2 - 357
⇒ \(x^2\) là số chẵn; \(x\) \(\in\) P ⇒ \(x\) = 2
Thay \(x\) = 2 vào biểu thức \(x^2\) + 357 = y2 ta có:
22 + 357 = y2
y2 = 361
y = \(\pm\) 19
Vì y là số nguyên tố nên y = 19
Kết luận hai số nguyên tố \(x\); y thỏa mãn đề bài là:
(\(x\); y) = (2; 19)