https://olm.vn/hoi-dap/question/850271.html

dk bn tự xd nhé

\(\left\{{}\begin{matrix}1+\dfrac{1}{x+y}=\dfrac{2}{\sqrt{3x}}\left(1\right)\\1-\dfrac{1}{x+y}=\dfrac{4\sqrt{2}}{\sqrt{7y}}\left(2\right)\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}2=\dfrac{2}{\sqrt{3x}}+\dfrac{4\sqrt{2}}{\sqrt{7y}}\left(1\right)+\left(2\right)\\\dfrac{2}{x+y}=\dfrac{2}{\sqrt{3x}}-\dfrac{4\sqrt{2}}{\sqrt{7y}}\left(1\right)-\left(2\right)\end{matrix}\right.\)

nhân vế vs vế 2 hpt trên \(\dfrac{4}{x+y}=\left(\dfrac{2}{\sqrt{3x}}-\dfrac{4\sqrt{2}}{\sqrt{7y}}\right)\left(\dfrac{2}{\sqrt{3x}}+\dfrac{4\sqrt{2}}{\sqrt{7y}}\right)\)

\(\Leftrightarrow\dfrac{4}{x+y}=\dfrac{4}{3x}-\dfrac{32}{7y}\)

\(\Leftrightarrow\dfrac{1}{x+y}=\dfrac{1}{3x}-\dfrac{8}{7y}\)

đến đây bn giải nốt nhé

mk nghĩ đề bài như này ms đúng chứ

\(\dfrac{a+b}{\sqrt{a\left(3a+b\right)}+\sqrt{b\left(3b+a\right)}}\ge\dfrac{1}{2}\)

vs a,b>0

cm \(vt=\dfrac{2\left(a+b\right)}{\sqrt{4a\left(3a+b\right)}+\sqrt{4b\left(3b+a\right)}}\)

\(\ge\dfrac{2\left(a+b\right)}{\dfrac{4a+3a+b}{2}+\dfrac{4b+3b+a}{2}}=\dfrac{2\left(a+b\right)}{\dfrac{8\left(a+b\right)}{2}}=\dfrac{1}{2}\)(dpcm)

dau = xay ra khi a=b>0

Read and answer the question:

Falling is common type of accident for young children at home. Your baby brother or sister may fall off a bed or a sofa. He or she may also fall down the stairs. The following tips can help to keep your baby brother or sister safe:

- Make sure he or she can’t roll off the bed.

- Make sure he or she can’t open any windows.

- Don’t let him or her go near the stairs.

- Don’t let him or her out on the balcony.

What should we do when a child is on the bed or a sofa?

10   d c m 2   2 c m 2   =   . . . . . . c m 2

A. 1002  c m 2

B. 102  c m 2

C. 120  c m 2

bạn vào tập đề này nha

https://drive.google.com/file/d/1qghW8c9otoJZ6bP-WxY9CqZDsWMf3X7H/view?ts=5a07dbd3

bài này trong đề thi hsg toán 9 huyện đan phượng năm nay nhé bạn