Toán Lớp 5: Tìm x biết (1/2+1/4+1/8+1/16):x=1/2+1/6+1/12+1/20+-+1/132.Giúp mình vs????

Question

Toán Lớp 5:  Tìm x biết  (1/2+1/4+1/8+1/16):x=1/2+1/6+1/12+1/20+....+1/132.Giúp mình vs????

thanhthuythu · Answer

( 1/2 + 1/4 + 1/8 + 1/16) : x = 1/2 + 1/6 + 1/12 + 1/20 + .... + 1/132   ( 8/16 + 4/16 + 2/16 + 1/16) : x = 1/(1.2) + 1/(2.3) + 1/3.4) + 1/(4.5) + .... + 1/(11.12)   15/16 : x = 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + .... + 1/11 - 1/12   15/16 : x = 1 - 1/12   15/16 : x = 11/12   x = 15/16 : 11/12   x= 45/44   Vậy x = 45/44

behocgioitoan · Answer

( 1/2 + 1/4 + 1/8 + 1/16 ) : x = 1/2 + 1/6 + 1/12 + 1/20 + ... + 1/132   ( 8/16 + 4/16 + 2/16 + 1/16 ) : x = 1/2 + 1/6 + 1/12 + 1/20 + ... + 1/132   15/16 : x = 1/{1 &times; 2} + 1/{2 &times; 3} + 1/{3 &times; 4} + 1/{4 &times; 5} + ... + 1/{11 &times; 12}   15/16 : x = 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + ... + 1/11 - 1/12   15/16 : x = 1/1 - 1/12   15/16 : x = 11/12               x = 15/16 : 11/12               x = 45/44   Vậy , x = 45/44    #dtkc