(1/2+1/6+1/12+1/20+...+1/72) : X = 3/4
(1/1x2+1/2x3+1/3x4+1/4x5+...+1/7x8) : X = 3/4
(1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+...+1/7-1/8) : X = 3/4
(1/1-1/8) : X = 3/4
7/8 : X = 3/4
X = 7/8 : 3/4
X = 7/6
a) N = 1/2 + 1/6+ 1/12 + 1/20 + 1/30 +1/42 + 1/56 + 1/72 +1/90
b) 5/8 + 2/9 -2/5 + 3/8 + 4/9 + 1/3 - 3/5 =
c) 4 1/5 + 5 1/3 - 2 2/3 x 3 1/5 + 9/25 : 9/20 =
Tìm x (nhanh):
a, 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90 + x = 3/5
b, 2/3.5 + 2/5.7 + ... + 2/13.15 + x = 1/3
c, 1/2 + 1/6 + 1/12 + 1/20 + ... + 1/x( x + 1) = 9/10
Ở cậu b dấu chấm là dấu nhân đấy nhé!!!
Giải ra nhé!!!
Tinh hon so sau :
1 1/2 +2 1/6 + 3 1/12 + 4 1/20 + 5 1/30 + 6 1/42 + 7 1/56 + 8 1/72 +9 1/90 +1/10
a ) 12,8 x 195 + 12,8 x 804 + 12,8
b) 1/2 +1/6 + 1/12+ 1/20+ 1/30 +1/42 +1/56 +1/72+ 1/90
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72=????
tinh tong A=1/2+1/6+1/12+1/20+...+1/72+1/90
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 = ?
1/90-1/72-1/56-1/42-1/30-1/20-1/12-1/6-1/2
1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90