Toán Lớp 6: 1/15 +1/35 +1/63 +1/99 +1/143 +1/95 Giúp mink với ạ

Question

Toán Lớp 6:  1/15 +1/35 +1/63 +1/99 +1/143 +1/95 Giúp mink với ạ

ngoclanhoa · Answer

1/15 + 1/35 + 1/63 + 1/99 + 1/143 + 1/195   = 1/( 3 . 5) + 1/( 5 . 7) + 1/( 7 . 9) + 1/( 9 . 11) + 1/( 11 . 13) + 1/( 13 . 15)   = 1/2 . ( 2/( 3 . 5) + 2/( 5 . 7) + 2/( 7 . 9) + 2/( 9 . 11) + 2/( 11 . 13) + 2/( 13 . 15))   = 1/2 . ( 1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11 + 1/11 - 1/13 + 1/13 - 1/15)   = 1/2 . [ 1/3 - ( 1/5 - 1/5) - ( 1/7 - 1/7) - ( 1/9 - 1/9) - ( 1/11 - 1/11) - ( 1/13 - 1/13) - 1/15]   = 1/2 . ( 1/3  - 0 - 0  - 0 - 0 - 1/15)   = 1/2 . ( 1/3 - 1/15)   = 1/2 . ( 5/15 - 1/15)   = 1/2 . 4/15   = 2/15   #caty09

danvanthu · Answer

text {Mon}   1/15+1/35+1/63+1/99+1/143+1/195   =1/3.5+1/5.7+1/7.9+1/9.11+1/11.13+1/13.15   =1/2.(2/3.5+2/5.7+2/7.9+2/9.11+2/11.13+2/13.15)   =1/2.(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15)   =1/2.(1/3-1/15)   =1/2 . 4/15   =2/15