\(1mm=1.10^{-3}m\\ S=\dfrac{d^2\pi}{4}=\dfrac{\left(1.10^{-3}\right)^2.3,14}{4}=7,85.10^{-7}\\ R=\rho\cdot\dfrac{l}{S}=0,4.10^{-6}\cdot\dfrac{4}{7,85.10^{-7}}\approx2,04\Omega\)

  Em dùng công thức toán học để ghi đề bài sẽ giúp hiểu đúng đề được em nhé. 

With the developments of our country,having a life skill play a vital part to teenagers in Vietnam.In my opinion,communication is one of the most important skills that they really need.First of all,in a modern world,communication is more neccessary,having this skill,youngsters can easily get a good job in the future.As i see,almost every one who is good at communicating achieve a great success in their lives.Secondly,this skill will make you feel more confident in front of crowd,so you can show your ability without any difficult.Everyone will also believe in you.Moreover,communication skill even help you to make friends.It's can't be denied that speech is the fastest way to connect people with each other.Therefore,the better you are at communicating,the more friends you will have.Inconclusion,in my point of view,communicating is a really vital life skill.