write about your health (topic) [mấy bn kô cảm vì cô mình chỉ ghi vậy nên chi tiết mình ko bt]
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DS
6 tháng 7 2016
a)49.7.73
=72.71.73
=76
b)98:32
98=(32)8
=316:32
=314
Chúc em học tốt^^
NT
2
24 tháng 10 2021
\(4,=\dfrac{6\left(\sqrt{2}-\sqrt{3}-3\right)}{5-2\sqrt{6}-9}=\dfrac{6\left(\sqrt{2}-\sqrt{3}-3\right)}{-4-2\sqrt{6}}\\ =\dfrac{3\left(3-\sqrt{2}-\sqrt{3}\right)}{2+\sqrt{6}}=\dfrac{\left(9-3\sqrt{2}-3\sqrt{3}\right)\left(\sqrt{6}-2\right)}{2}\\ =\dfrac{9\sqrt{6}-18-6\sqrt{3}+6\sqrt{2}-9\sqrt{2}+6\sqrt{3}}{2}\\ =\dfrac{9\sqrt{6}-3\sqrt{2}-18}{2}\)
\(7,=\dfrac{\sqrt{3}\left(\sqrt{3}+2\right)}{\sqrt{3}}+\dfrac{\sqrt{2}\left(\sqrt{2}+1\right)}{\sqrt{2}+1}-2-\sqrt{3}\\ =\sqrt{3}+2+\sqrt{2}+1-2-\sqrt{3}=1+\sqrt{2}\)
\(10,\dfrac{1}{\sqrt{a}+\sqrt{a+2}}=\dfrac{\sqrt{a}-\sqrt{a+2}}{a-a-2}=\dfrac{\sqrt{a-2}-\sqrt{a}}{2}\)
Do đó \(\dfrac{1}{\sqrt{1}+\sqrt{3}}+\dfrac{1}{\sqrt{3}+\sqrt{5}}+...+\dfrac{1}{\sqrt{47}+\sqrt{49}}\)
\(=\dfrac{\sqrt{3}-\sqrt{1}+\sqrt{5}-\sqrt{3}+...+\sqrt{49}-\sqrt{47}}{2}=\dfrac{-1+\sqrt{49}}{2}=\dfrac{7-1}{2}=3\)
24 tháng 10 2021
10, \(\dfrac{1}{\sqrt{1}+\sqrt{3}}+\dfrac{1}{\sqrt{3}+\sqrt{5}}+...+\dfrac{1}{\sqrt{17}+\sqrt{19}}=\dfrac{\sqrt{1}-\sqrt{3}}{\left(\sqrt{1}+\sqrt{3}\right)\left(\sqrt{1}-\sqrt{3}\right)}+\dfrac{\sqrt{3}-\sqrt{5}}{\left(\sqrt{3}+\sqrt{5}\right)\left(\sqrt{3}-\sqrt{5}\right)}+...+\dfrac{\sqrt{17}-\sqrt{19}}{\left(\sqrt{17}+\sqrt{19}\right)\left(\sqrt{17}-\sqrt{19}\right)}=\dfrac{1-\sqrt{3}+\sqrt{3}-\sqrt{5}+...+\sqrt{17}-\sqrt{19}}{-2}=-\dfrac{1-\sqrt{19}}{2}\)
29 tháng 1 2016
Mình cũng gặp TH giống như cậu nhưng mình nghĩ là khi lớn lên các bạn cậu sẽ thay đổi suy nghĩ mà thôi. Vì vậy bạn đừng buồn nữa nhé!
tham khảo
Today, there are more and more dangerous diseases. As a result, it is very important to stay healthy. Firstly, you should have a balanced diet. For example, you should eat vegetables and fruits and avoid fast food. In addition, you should not drink coffee, beer or alcohol because they are very harmful. Second, regular exercise is also a way to stay healthy. For example, you could play volleyball, go for a walk, or go swimming in the morning. Furthermore, exercise will make you healthier, more active and prevent many diseases. Last but not least, you should get enough sleep. Better to get 6 to 8 hours of sleep a day as it will boost your spirits in the morning. In particular, don't go to bed late or watch TV overnight. In short, there are many ways to stay healthy, but the above are the most popular and easiest to do.
Tham khảo
To have a good health, especially for your eyes, you should have a balanced diet. For instant, you had better eat vegetables and fruits whose colors are yellow or orange. The reason is that they contains lots of vitamins that are good for health. Secondly, you should keep a distance at least 35 cm when reading a book or sit correctly when working. Last but not least, you should take enough sleep. You’d better sleep at least 6 or 8 hours a day because it will boost your mind. Moreover, do not go to bed late or watch TV over night.