ĐK xdinh là
$2\sin^2x - m\sin x + 1 > 0$
Ta cần tập xdinh là $\mathbb{R}$ nên
$2\sin^2x - m\sin x + 1 > 0$ với mọi $x \in \mathbb{R}$
Đặt $t = \sin x$, suy ra $t \in [-1, 1]$ và bptrinh trở thành
$2t^2 - mt + 1 > 0$
Để đúng với mọi $x$ thì
$\Delta < 0$
$<-> m^2 - 4.2.1 < 0$
$<-> m^2 < 8$
$<-> -2\sqrt2 < m < 2\sqrt2$.
Vậy $m \in (-2\sqrt2, 2\sqrt2)$.
Fill in the blanks with the suitable words in the box. check-in luggage entertainment system business district alarm call check-in time 1. In a hotel you can phone the reception from your room for a(n)_______. 2. You should arrive at a hotel before_______. 3. You want to go to the______ , but you are not sure exactly where it is so you can call a taxi. 4. Last week he had three pieces of___________ but he was allowed only one. 5. On a plane you can watch an in-flight film, but you can't make the ________ work.
Giúp mình giải câu 4,5 vs . pleaseeee :((
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Đặc điểm khí hậu . Các môi trường tự nhiên châu âu
Người ta đào 1 bể ngầm hình hộp chữ nhật dài 12m,rộng 6m sâu 2m.Đất đào lên 1m³ nặng 1,75 tấn được chở đi bằng xe có trọng tải 9 tấn mỗi chuyến.Hỏi phải dùng bao nhiêu chuyến xe mới chở hết số đất đó
Thật chắc chắn nhé! Câu này làm thế nào ạ?
5m vuông 7dm vuông = .........m vuông
Fill in the blanks with the suitable words from the box. handicrafts design quality return appearance skills costumes history There are many embroiders' villages in Viet Nam, but Quat Dong village in Ha Noi is widely known for its products of high (1) Embroidery has been developing around here since the 17th century. In the past, local skilled artisans were chosen to make sophisticated embroidered (2) for the Vietnamese King. The first man who taught the local people how to embroider was Dr. Le Cong Hanh, who lived during the Le dynasty. He learned how to embroider while on a trip to China as an envoy, and taught the villagers of Quat Dong upon his (3) . Although these (4) eventually spread across the country, the Quat Dong's artisans' creations are still the most appreciated. In order to create beautiful embroideries, an artisan must be patient, careful and have an eye for (5) , along with clever hands. Nowadays, Quat Dong products may range from clothes, bags, pillowcases, to paintings and decorations, which are exported to many countries.
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