Register Now

Login

Lost Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: 1/1.3=1/3.5+1/5.7+…+1/(2x-1).(2x+1)=49/99 Tìm x nka mng nhanh hộ=((

Toán Lớp 6: 1/1.3=1/3.5+1/5.7+…+1/(2x-1).(2x+1)=49/99 Tìm x nka mng nhanh hộ=((

Comments ( 2 )

  1. Sửa lại đề : 
    1/(1.3) + 1/(3.5) + 1/(5.7) + … + 1/((2x-1).(2x+1)) = 49/99
    Bài làm :
    1/(1.3) + 1/(3.5) + 1/(5.7) + … + 1/((2x-1).(2x+1)) = 49/99
    => 2 . (1/(1.3) + 1/(3.5) + 1/(5.7) + … + 1/((2x-1).(2x+1)) ) = 2 . 49/99
    => 2/(1.3) + 2/(3.5) + 2/(5.7) + …. + 2/((2x-1).(2x+1)) = 98/99
    => 1 – 1/3 + 1/3 – 1/5 + 1/5 – 1/7 + ….  + 1/(2x-1) – 1/(2x+1) = 98/99
    => 1 – 1/(2x+1) = 98/99
    => 1/(2x+1) = 1 – 98/99
    => 1/(2x+1) = 1/99
    => 2x + 1 = 99
    => 2x= 98
    => x = 49
    Vậy x = 49
     

  2. Giải đáp + Lời giải và giải thích chi tiết:
    1/1.3+1/3.5+1/5.7+…+1/((2x-1)(2x+1))=49/99
    =>1/2[2/1.3+2/3.5+2/5.7+…+2/((2x-1)(2x+1))]=49/99
    =>1-1/3+1/3-1/5+1/5-1/7+…+1/(2x-1)-1/(2x+1)=49/99:1/2
    =>1-1/(2x+1)=49/99 .2
    =>1-1/(2x+1)=98/99
    =>1/(2x+1)=1-98/99
    =>1/(2x+1)=99/99-98/99
    =>1/(2x+1)=1/99
    =>2x+1=99
    =>2x=99-1
    =>2x=98
    =>x=98:2
    =>x=49
     

Leave a reply

222-9+11+12:2*14+14 = ? ( )

About Linh