1/2 . A=1/42+1/56+1/72+1/90+...+1/420
1/2 . A=1/6.7+1/7.8+1/8.9+1/9.10+...+1/20.21
1/2 .A=1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+....+1/20-1/21
1/2 . A=1/6-1/21
1/2 .A=5/42
A=5/42:1/2
A=5/21
Chúc bạn học giỏi nhớ tick cho mình nhé
A=1/21+1/28+1/36+1/45+....+1/210
Tính:\(A=\dfrac{1}{21}+\dfrac{1}{28}+\dfrac{1}{36}+\dfrac{1}{45}+...+\dfrac{1}{210}\)
Huhu giúp mik gấp nhé
Trưa mik thi rồi
Á huhu
Bài 6 tính
\(A=\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{10}}\)
\(F=\dfrac{1}{15}+\dfrac{1}{21}+\dfrac{1}{28}+...+\dfrac{1}{190}\)
\(G=\dfrac{12}{84}+\dfrac{12}{210}+\dfrac{12}{390}+...+\dfrac{12}{210}\)
Tính
1. 3/4 + 3/4.7 + 3/7.10 + 3/ 10.13 + 3/13.16 + 3/16.19 + 3/19.22 + 3/22.25
2. A = ( 1 - 1/21 ) * ( 1 - 1/28 ) * ( 1 - 1/36 ) *....* ( 1 - 1/1326 )
\(\dfrac{1}{21}+\dfrac{1}{28}+\dfrac{1}{36}+...+\dfrac{1}{x.\left(x+1\right):2}=\dfrac{2}{9}\)
Tính giá trị của biểu thức, tính nhanh nếu có thể:
21) ( 1 + 1/3 ) . ( 1 + 1/8 ) . ( 1 + 1/15 ) . ...... ( 1+ 1/9999)
22) A = \(\frac{38}{25}+\frac{9}{10}-\frac{11}{15}+\frac{13}{21}-\frac{15}{28}+\frac{17}{36}-......+\frac{197}{4851}-\frac{199}{4950}\)
tìm x,biết:
\(\dfrac{1}{21}+\dfrac{1}{28}+\dfrac{1}{36}+........+\dfrac{2}{x\left(x+1\right)}=\dfrac{2}{9}\)
Tìm x :
a) \(\frac{1}{5\cdot8}+\frac{1}{8\cdot11}+...+\frac{1}{x\left(x+3\right)}=\frac{101}{1540}\)
b) \(\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+...+\frac{2}{x\left(x+1\right)}=\frac{2}{9}\)
Câu 1:Tính A \(A=\left(1-\frac{1}{21}\right)\left(1-\frac{1}{28}\right)\left(1-\frac{1}{36}\right).....\left(1-\frac{1}{1236}\right)\)
Câu 2:
1.Tìm số nguyên x biết : \(\left|x^2-2\right|+\left|2-x^2\right|=28\)
2.Tìm số dư của \(A=776^{776}+777^{777}+778^{778}\) khi chia cho 3
