Câu 23: A

Câu 24: C

23.

\(\Delta'=m^2-\left(m^2-1\right)=1>0;\forall m\)

\(\Rightarrow\) Pt luôn có 2 nghiệm pb với mọi m

24.

Pt đã cho có 2 nghiệm trái dấu khi:

\(ac< 0\Leftrightarrow\left(m^2+2020\right)\left(m-2021\right)< 0\)

\(\Leftrightarrow m< 2021\Rightarrow\) có 2020 giá trị nguyên dương

25.

\(y=4x^2-3+\dfrac{9}{x^2}=4x^2+\dfrac{9}{x^2}-3\ge2\sqrt{4x^2.\dfrac{9}{x^2}}-3=9\)

Câu 23: A

Câu 24: C

1.A
2.A
3.B
4.C
5.B
6.C
7.A
8.A
9.B
10.A
11.B
12.A
13.C
14.B
15.B
16.A
17.A
18.A
19.A
20.C

sao dài thế

1. so
2. such
3. such
4. such
5. so
6. such
7. so
8. such (a great success ?)
9. enough
10. too
.
3. The patient was so weak that he couldn't get up.
4. This room is so dark that I can't study.
5. This room isn't big enough for us to take the meeting.
6. The test was not easy for us to do it.
7. The map is too old for me to read.
8. He didn't speak slowly enough for us to hear him well.
.
1. That woman was so tall that she could....
2. This could is too big for me to wear.
3. The coffee was so strong that she couldn't....
4. That bag was so heavy that none of....
5. The stadium is big enough to hold 60 000 people.
6. The question was too hard for us to answer.
7. The TV program is so exciting that the children....
8. You are not old enough to drive that car.

6. B

7. D

8. C

9. B

Ko thay đổi

2 bài nào vậy??

10. C

11. C

1. If you use compact light bulbs, you will save a lot of energy

2. English is spoken in the world by many people

1 If you use compact light bulbs, you will save a lot of energy

2 English is spoken in the world