`\sqrt{4x^2 + 4x + 1} = 7`
`⇔ \sqrt{(2x + 1)^2} = 7`
`⇔ |2x + 1| = 7`
`⇒` \(\left[ \begin{array}{l}2x + 1 = 7\\2x + 1 = -7\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x = 3\\ x = -4\end{array} \right.\)
`Vậy S = {3 ; -4}`
Đáp án: + Giải thích các bước giải:
$ \sqrt{4x² + 4x + 1} = 7$
$\sqrt{(2x + 1)²} = 7$
$|2x + 1| = 7$
$⇒ 2x + 1 = ± 7$
\(\left[ \begin{array}{l}2x + 1=7\\2x + 1=-7\end{array} \right.\)
\(\left[ \begin{array}{l}x=3\\x=-4\end{array} \right.\)
B. Join the sentences, using relative clauses. (Kết hợp câu, dùng mệnh đề quan hệ.) 1. A girl answered the phone. She told me you were out. 2. The chair was broken two days ago. The chair has now been repaired. 3. I saw some people. Their car had broken down. 4. I recently went back to my hometown, I was born there.
chỉ mk cách đếm nhanh số cực trị vs cho hàm số f(x) có đạo hàm f'(x) = x³(x-1)(x-2) , ∀x ∈R số điểm cực trị của hàm số là
Helllllllllllllllllllll meeeeeeeeeee
Ex1. Choose the correct answer. 1. When I started working here I needed a lot of help, but now I used to do/ get used to doing/ am used to doing all the work on my own. 2. He used to read/ was used to reading/ got used to reading several books a month, but he doesn't have time any more. 3. We were surprised to see her driving – she got used to driving/ didn’t use to drive/ was used to driving when we first met her. 4. Don't worry, it's a simple program to use. You are used to/ will get used to/ used to use it in no time, I'm sure. 5. When I had to commute to work every day I used to get up/ used to getting up very early. 6. I'm afraid I'll never used to live/ get used to living/ got used to living in this place. I simply don't like it and never will. 7. Whenever we came to Coventry we always used to stay/ got used to staying in the Central Hotel. We loved it. 8. When Pete Smith was the head of our office everything got used to be/ was used to being/ used to be well organized. Now it's total chaos here. 9. Mr Lazy was shocked when he joined our busy company because he wasn’t used to/ didn’t use to doing much work every day. 10. At first the employees didn't like the new open-space office, but in the end they get used to/ got used to/ are used to it. Ex2. Complete the sentences using used to or be used to. 1. How did you get (work)…………………………. in the middle of this mess? 2. I need some time to (live) …………………………. in this town. 3. He (be) …………………………. but now he’s thin. 4. He (not/ deal) …………………………. with animals, so he’s a bit scared of the dogs. 5. He (do) …………………………. a lot of exercise, so a ten-mile walk is easy for him. 6. He doesn’t have any problems getting to work at 7:00 in the morning because she (get) …………………………. up early. 7. Before he became ill, he (play) …………………………. tennis every morning. 8. Today many children (watch) …………………………. TV for hours instead of doing their homework. 9. We (go) …………………………. shopping twice a month, but now we can’t afford it. 10. My parents (travel) …………………………. to other countries when they were young, but now they (go) …………………………. to places that are nearby. 11. Once grandparents, parents and children (live) …………………………. together, but now grandparents (live) …………………………. by themselves.
Tứ giác ABCD có A = B, BC = AD a)Chứng minh ABCD là hình thang cân b) Cho biết AC ⊥BD và đường cao AH = 4cm Tính AB+CD giúp mình với mình cần gấp
mn ơi giúp mình với chiều nộp rồi cảm ơnnnn
Giải thật sự chi tiết hộ em câu này ạ
3.in / in/ city/ better/ the / is/ in /than / country/ convenient / than / is. Sắp xếp câu cho hợp lý.
A. Finish each of the following sentences in such a way that it is similar in meaning to the original sentence. (Hoàn chỉnh mỗi câu sau theo cách nào đó để nó có nghĩa tương tự với câu gốc.) 1. Someone has cleaned the windows. 2. They are going to build a supermarket in this area. 3. They say Lan won a special prize. 4. You won't know what to do unless you listen carefully. 5. I can’t give you a lift because I don’t have a car. 6. We got lost because we didn’t bring a city map.
Làm câu 3 giúp mik với CẦN GẤP Ạ
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