bn cần z cứ hỏi đi đã nào

các bn giúp mink nha

Trả lời: 

\(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+9\right)+\left(x+10\right)=240\)

\(\Leftrightarrow\left(x+x+x+...+x+x\right)+\left(1+2+3+...+9+10\right)=240\)

\(\Leftrightarrow10x+\left(10+1\right)\times\left[\left(10-1\right)\div1+1\right]\div2=240\)

\(\Leftrightarrow10x+11\times10\div2=240\)

\(\Leftrightarrow10x+55=240\)

\(\Leftrightarrow10x=185\)

\(\Leftrightarrow x=18,5\)

Vậy \(x=18,5\)

( x+1 )+( x+2 )+...+( x+10 ) = 240

= x+1 + x+2 + x+3 +...+ x+9 + x+10 = 240

= ( x+x+x+...+x ) + ( 1+2+3+...+9+10 ) = 240

= 10.x + 55 = 240

   10.x = 240-55

   10.x = 185

     x  = 185 : 10

    x  = 18,5

Dễ thấy : \(\dfrac{2017}{2018}>\dfrac{2017}{2018+2019}\)  ; \(\dfrac{2018}{2019}>\dfrac{2018}{2018+2019}\)

\(\Rightarrow A=\dfrac{2017}{2018}+\dfrac{2018}{2019}>\dfrac{2017+2018}{2018+2019}=B\)

Ở sách nào vậy bạn

Among many programs and channels available on TV these days such as the current news programs, sport programs, entertaining programs, educational programs and movie programs, etc, I the program "the World of Animals" most.

This program is usually shown on VTV2 everyday at 8.30 in the evening. It often lasts about 45 minutes. In this program, stories of the life of many animals in the world are told in a very lively way. For example, people can watch films about monkeys, snakes, tigers, insects, birds, sea turtles, sharks etc and even the penguins and the polar bears in the far North. While watching these films, I find the everyday life activities and habits of these animals very interesting and full mysteries. In addition, I also learn that it is very important to protect these animals and their living environments because they are part of our valuable natural world. Watching this program makes me very well informed and relaxed after a day of work.