Question

(\(\frac{1}{1.2}\)+\(\frac{1}{2.3}\)+\(\frac{1}{3.4}\)+...+\(\frac{1}{8.9}\)+\(\frac{1}{9.10}\)) .100-[\(\frac{5}{2}\):(x+\(\frac{206}{100}\))] :\(\frac{1}{2}\)=89

Answer 1

giúp mk nha. mk sẽ k cho bn nào trả lời giúp mk mà đúng

Answer 2

 (1/1*2+1/2*3+1/3*4+...+1/8*9+1/9*10)*100-[5/2:(x+206/100)]:1/2=89

Đặt A=1/1*2+1/2*3+1/3*4+...+1/8*9+1/9*10

      A=1-1/2+1/2-1/3+1/3-1/4+...+1/8-1/9+1/9-1/10

      A=1-1/10

      A=9/10

=>(1/1*2+1/2*3+1/3*4+...+1/8*9+1/9*10)*100-[5/2:(x+206/100)]:1/2=89

=9/10*100-[5/2:(x+206/100)]:1/2=89

  90-[5/2:(x+206/100)]:1/2=89

  5/2:(x+206/100):1/2=90-89

  5/2:(x+206/100):1/2=1

   x+206/100:1/2=5/2:1

   x+206/100:1/2=5/2

   x+103/25=5/2

   x=5/2-103/25

   x=-81/50