Giải:

Để đa thức có nghiệm thì:

\(x-\dfrac{1}{2}x^2=0\)

\(\Leftrightarrow x\left(1-\dfrac{1}{2}x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\1-\dfrac{1}{2}x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\end{matrix}\right.\)

Vậy ...

Ta có : 4²⁴ = ( 2² )²⁴ = 2⁴⁸

           32²³= ( 2⁵ )²³ = 2¹¹⁵

Vì 2⁴⁸< 2¹¹⁵ nên 4²⁴ < 32²³

Mỗi giờ kim phút quay được 1 vòng, kim giờ quay được  vòng, do đó trong một giờ kim phút quay nhanh hơn kim giờ là:

1-  =  (vòng)

 Vậy nếu ta coi vận tốc kim giờ là 1 phần thì vận tốc kim phút bằng 12 phần như thế; nên hiệu vận tốc  là 1-  =  ( vòng đồng hồ/ giờ) .

Lúc 1 giờ hai kim đồng hồ cách nhau một khoảng  vòng (Hiệu quãng đường) nên thời gian gần nhất để  hai kim đồng hồ trùng nhau là:

(giờ)

65/91= y- 5/133

nhân chéo =>65.133=91.(y-5)

=>8645 = 91.(y-5)

=>y-5 = 8645:91

=> y- 5 = 95  => y= 95 +5 = 100 

7. There isn't much rain to make the crops better.
The crops aren't___better because of not being much rain. (câu này mình không chắc lắm)________________________
8. Why don't you have your hair cut?
She suggests ___I should cut my hair_____________________
9. I think you should apply for that job.
If____I were you, I would apply for that job_____________________________
10. Because of her carelessness, Lan broke the glass.
Because Lan _______was careless, she broke the glass___________________________-
11. BKAV is a program. Its performance is really good.
The program __________whose performance is really good is BKAV___________________________
12. They stopped going out with each other two years ago.
They haven't ___gone out with each other for two years____________________________________
13. About thirty million people are watching this program.
This program_____is being watched by thirty million people_______________________________
14. You are tired because you often stay up late.
If you ______didn't stay up late, you wouldn't be tired____________________________
15. The students are working in a laboratory with a lot of chemicals.
The laboratory_____which the students are working in has a lot of chemicals (câu này cũng không chắc lắm)
16. The last time I saw him was two days ago.
I haven't_____seen him for 2 days_____________________________
17. They have painted their house blue and white.
Their house _____has been painted blue and white__________________________
18. Lan is the best student in our class.
Nobody___in our class is better than Lan_____
19. We are studying in a very large classroom now.
The classroom ____which we are studying in now is very large_______
20. We haven't had a party since last Christmas.
The last time _____we had a party was last Christmas________________________________
21. They haven't decided the exact time of the match yet.
The exact time ______of the match hasn't been decided yet____________________________
22. It was after midnight, but we did not feel tired.
Although________it was after midnight, we didn't feel tired__________________________
23. They stayed in a very luxurious hotel last summer.
The hotel_____which they stayed in last summer is very luxurious____________________________
24. The last time they played tennis was two years ago.
They haven't_____played tennis for 2 years______________________________

câu 2 là tăng thêm 16 lần

9²⁰<27¹³ (vì cơ số lớn hơn cho nên lũy thừa đó cũng lớn hơn)

Cho mình hỏi số 2 ở đâu ra vậy

n+5 chia hết cho n-2

=> n-2+7 chia hết cho n-2. ma n-2 chia hết cho n-2

=>7 chia hết cho n-2

=> n-2 thuộc { -7; -1; 1; 7}

=> n thuộc {-5;1;3;9}

Vậy n thuộc {-5;1;3;9}

Giải:

\(A=\sqrt{13+30\sqrt{2+\sqrt{9+4\sqrt{2}}}}\)

\(\Leftrightarrow A=\sqrt{13+30\sqrt{2+\sqrt{\left(2\sqrt{2}\right)^2+4\sqrt{2}+1^2}}}\)

\(\Leftrightarrow A=\sqrt{13+30\sqrt{2+\sqrt{\left(2\sqrt{2}+1\right)^2}}}\)

\(\Leftrightarrow A=\sqrt{13+30\sqrt{2+2\sqrt{2}+1^2}}\)

\(\Leftrightarrow A=\sqrt{13+30\sqrt{\left(\sqrt{2}\right)^2+2\sqrt{2}+1^2}}\)

\(\Leftrightarrow A=\sqrt{13+30\sqrt{\left(\sqrt{2}+1\right)^2}}\)

\(\Leftrightarrow A=\sqrt{13+30\left(\sqrt{2}+1\right)}\)

\(\Leftrightarrow A=\sqrt{5^2+2.5.3\sqrt{2}+\left(3\sqrt{2}\right)^2}\)

\(\Leftrightarrow A=\sqrt{\left(5+3\sqrt{2}\right)^2}\)

\(\Leftrightarrow A=5+3\sqrt{2}^2\)

Vậy ...

Câu b bị sai đề hay sao đó bạn, bạn kiểm tra lại rồi ghi lại đề nhé!