Một lớp học có 45 học sinh,trong một bài kiểm tra tất cả học sinh đều được điểm 8 hoặc điểm 9.Tổng số điểm của cả lớp là 379 điểm.Khi đó số học sinh đạt điểm 8 là 26 học sinh  .

999

378 tick

2. Phương trình có nghiệm kép:

\(\Leftrightarrow\Delta'=0\\ \Leftrightarrow m^2-\left(m-1\right).3=0\\ \Leftrightarrow m^2-3m+3=0\left(1\right)\)

Giải phương trình \(\left(1\right)\) ta được:

\(\Delta_m=3^2-4.1.3=-3< 0\)

\(\Rightarrow\) Phương trình \(\left(1\right)\) vô nghiệm.

Vậy không có giá trị nào của \(m\) thoản mãn để phương trình có nghiệm kép.

1. Phương trình có hai nghiệm phân biệt:

\(\Leftrightarrow\Delta>0\\ \Leftrightarrow5^2-4.m.\left(-3\right)>0\\ \Leftrightarrow25+12m>0\\ \Leftrightarrow12m>-25\\ \Leftrightarrow m>\dfrac{-25}{12}\)

bn nhấn vào đúng 0 sẽ ra đáp án

Complete the sentences with "and, so, but, before, then, after,, because":

I got out of the car and walked into the house.

Environmental pollution is a term that (1) refers to all the ways by which man pollutes his surroundings. Man dirties the air with (2) exhaust gases and smoke, (3) poisons the water with...

1. Four countries have been visited (visit) by John so far.

2. London has (have) a population of eight million people.

3. The Statue of Liberty in New York in a moument which symbolizes (symbolize) freedom.

4. He(A) said he would go(B) to(C) England next week(D).

=> the next week

5. Nam(A) wishes(B) he can speak(C) English fluently(D).

=> could speak

thi tiếng anh j vậy bạn 

Ex1: Complete the conditional sentences, using the given information:

1. You should take exercise regularly because it is the way to get fit.

=> If you take exercise regularly, you will get fit.

2. I can't look the word up because I don't have a dictionary.

=> If I had a dictionary, I could look the word up.

3. I don't have his phone number, so I don't phone him.

=> If I had his phone number, I would phone him.

4. You may want a help, just give me a ring.

=> If you want a help, you must give me a ring.

5. It is raining, so we won't finish the game.

=> If it weren't raining, we would finish the game.