Ân Thiên
5 giờ trước (23:50)

Giúp mình vớiii

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𝐆𝐥𝐮𝐜𝐨𝐳𝐨 𝐝𝐚𝐲 𝐧𝐚𝐲
Thiếu tướng -
5 giờ trước (23:53)

nCO2 = 0.1 (mol) 

Ba(OH)2 + CO2 => BaCO3 + H2O 

0.1________0.1_____0.1

CM Ba(OH)2 = 0.1/0.2 = 0.5 M 

mBaCO3 = 0.1*197 = 19.7 (g) 

Chúc học tốt <3 

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𝐆𝐥𝐮𝐜𝐨𝐳𝐨 𝐝𝐚𝐲 𝐧𝐚𝐲
Thiếu tướng -
5 giờ trước (23:52)

Để loại bỏ được CO2 , SO2 ta dùng một chất vô cùng rẻ và dể tìm kiếm là : Ca(OH)2 để hấp thụ lại và tạo ra những chất không gây ô nhiễm môi trường. 

CO2 + Ca(OH)2=> CaCO3 + H2O

SO2 + Ca(OH)2 => CaSO3 + H2O

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Thanh Hoàng Thanh
Thiếu úy -
5 giờ trước (23:28)

Ta có: ^AKB là góc nội tiếp chắn nửa đường tròn (O)

=> ^AKB = 90  (t/c góc nội tiếp ).

Xét tứ giác HKBI ta có:

     ^HKI=900          (do  CD⊥AB tại I)

=> ^HKI + ^ HIB=180.

=> Tứ giác BKHI là tứ giác nội tiếp (dhnb).

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Thanh Hoàng Thanh
Thiếu úy -
5 giờ trước (23:31)

b) Xét TGiac AHI và Tgiac AKB có:

    ^AKB = ^AHI ( do cùng =90 độ)

    ^A chung

=> tam giác AHI đồng dạng với AKB (g - g)

=> AH/AB = AI/AK (cặp cạnh tg ứg tỉ lệ)

=> AH.AK = AI.AB

Mà AI; AB cố định

=> AH.AK không phụ thuộc vào vị trí điểm K (đpcm)

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Thanh Hoàng Thanh
Thiếu úy -
5 giờ trước (23:38)

Xét (O): Dây CD vuông góc AB tại I (gt)

=> I là TĐ của CD  và OA ( .....)

Xét Tứ giác MDNC có:

^MCN = 90 độ ( do ^MCN là góc nội tiếp chắn nửa đường tròn tâm O)

^CMD =90 độ ( vì CM vg góc MD)

^CND  =90 độ ( vì DN vg góc CB)

=>MNDC là hcn (dhnb)

=> CD và MN cắt nhau tại TĐ của mỗi đường (tc hcn)

Mà I là trung điểm của CD (cmt)

=> CD và MN cắt nhau tại I 

Mà  I thuộc AB (gt)

=> MN, AB, CD đồng quy (đpcm)

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Tan Thuy Hoang
Trung tá -
5 giờ trước (23:22)

1) Áp dụng bất đẳng thức AM - GM và bất đẳng thức Schwarz:

\(P=\dfrac{1}{a}+\dfrac{1}{\sqrt{ab}}\ge\dfrac{1}{a}+\dfrac{1}{\dfrac{a+b}{2}}\ge\dfrac{4}{a+\dfrac{a+b}{2}}=\dfrac{8}{3a+b}\ge8\).

Đẳng thức xảy ra khi a = b = \(\dfrac{1}{4}\).

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Nguyễn Việt Lâm
Trung tá -
5 giờ trước (23:54)

2.

\(4=a^2+b^2\ge\dfrac{1}{2}\left(a+b\right)^2\Rightarrow a+b\le2\sqrt{2}\)

Đồng thời \(\left(a+b\right)^2\ge a^2+b^2\Rightarrow a+b\ge2\)

\(M\le\dfrac{\left(a+b\right)^2}{4\left(a+b+2\right)}=\dfrac{x^2}{4\left(x+2\right)}\) (với \(x=a+b\Rightarrow2\le x\le2\sqrt{2}\) )

\(M\le\dfrac{x^2}{4\left(x+2\right)}-\sqrt{2}+1+\sqrt{2}-1\)

\(M\le\dfrac{\left(2\sqrt{2}-x\right)\left(x+4-2\sqrt{2}\right)}{4\left(x+2\right)}+\sqrt{2}-1\le\sqrt{2}-1\)

Dấu "=" xảy ra khi \(x=2\sqrt{2}\) hay \(a=b=\sqrt{2}\)

3. Chia 2 vế giả thiết cho \(x^2y^2\)

\(\dfrac{1}{x}+\dfrac{1}{y}=\dfrac{1}{x^2}+\dfrac{1}{y^2}-\dfrac{1}{xy}\ge\dfrac{1}{4}\left(\dfrac{1}{x}+\dfrac{1}{y}\right)^2\)

\(\Rightarrow0\le\dfrac{1}{x}+\dfrac{1}{y}\le4\)

\(A=\left(\dfrac{1}{x}+\dfrac{1}{y}\right)\left(\dfrac{1}{x^2}+\dfrac{1}{y^2}-\dfrac{1}{xy}\right)=\left(\dfrac{1}{x}+\dfrac{1}{y}\right)^2\le16\)

Dấu "=" xảy ra khi \(x=y=\dfrac{1}{2}\)

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Phương Dung
Thượng tá -
5 giờ trước (23:09)

People say that the students are eager to take part in the out - door activities. 

- It is said that the students are eager to take part in the out - door activities. 

- The students are said to be eager to take part in the out - door activities. 

They think that the traffic rules are strictly obeyed by the local people. 

- It is thought  that the traffic rules are strictly obeyed by the local people. 

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Thanh Hoàng Thanh
Thiếu úy -
5 giờ trước (23:09)
People say that the students are eager to take part in the out - door activities.- It is said that the students are eager to take part in the out - door activities. - The students is said to be eager to take part in the out - door activities. They think that the traffic rules are strictly obeyed by the local people.- It is thought that the traffic rules are strictly obeyed by the local people.- The traffic rules is thought to be strictly obeyed by the local people. 
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Đại tá -
5 giờ trước (23:08)

. People say that the students are eager to take part in the out - door activities.

- It....is said that the students are eager to take part in the out - door activities.....

- The students.are said to be eager to take part in the out - door activities.

They think that the traffic rules are strictly obeyed by the local people.

- It......is thought that the traffic rules are strictly obeyed by the local people....

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Đại tá -
5 giờ trước (23:07)

They think that he has died a natural death.

- It.is thought that he has died a natural death.

- He is thought to have died a natural death. 

They though that the students had cheated in the exam.

- It...was thought that the students had cheated in the exam...

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People say that John has left his home country two years ago.

- It....is said that John has left his home country two years ago.....

- John is said to have left his home country two years ago.

People knew that the boy was found in the forest.

- It..was known that the boy was found in the forest....

- The boy..was known to be found in the forest.

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Thanh Hoàng Thanh
Thiếu úy -
5 giờ trước (23:07)

They think that he has died a natural death.

- It is thought that he has died a natural death. 

- He is thought to have died a natural death. 

They though that the students had cheated in the exam.

- It was thought that the students had cheated in the exam.

- The students was thought to have cheated in the exam.

People say that John has left his home country two years ago.

- It is said that John has left his home country two years ago.

- John is said to have left his home country two years ago.

People knew that the boy was found in the forest.

- It was known that the boy was found in the forest. 

- The boy was known to have been found in the forest.

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