1/2+1/14+1/35+....1/527
E=1/2+1/14+1/35+1/65+...+1/527
E=1/2+1/14+1/35+1/65+...+1/527
Biểu thức nào sau đây có giá trị bằng biểu thức (35 + 65) x 527?
A. 35 + 65 x 527
B. 35 + 527 x 65 + 527
C. 35 x 527 + 65 x 527
D. 35 x 527 + 65
1. Tìm x : 1/2 + 1/14 + 1/35 +....+ 1/x(x+3):2 = 9/14
Mong các bạn giúp mình !
Ta có : \(\frac{1}{2}+\frac{1}{14}+\frac{1}{35}+...+\frac{1}{x\left(x+3\right):2}=\frac{9}{14}\)
\(\Rightarrow2\left(\frac{1}{4}+\frac{1}{28}+\frac{1}{70}+...+\frac{1}{x\left(x+3\right)}\right)=\frac{9}{14}\)
\(\Rightarrow2.\frac{1}{3}\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{x\left(x+3\right)}\right)=\frac{9}{14}\)
\(\Rightarrow\frac{2}{3}\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{9}{14}\)
\(\Rightarrow1-\frac{1}{x+3}=\frac{27}{28}\)
\(\Rightarrow\frac{1}{x+3}=\frac{1}{28}\)
=> x + 3 = 28
=> x = 25
a/ 1/2 + 5/6 + 11/12 + 19/20
b/ 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42
c/ (1-1/3) + (1-1/15) + (1-1/35) + (1-1/63)
d/ 1/2 + 5/6 + 11/12 + ... + 9899/9900
e/ 2/3 + 14/15 + 34/35 +62/63
f/ 2/3 + 14/15 + 34/35 + ... + 9998/9999
cái này tính cái gì thế
ko hiểu
D=1/2+1/14+1/35+.......+1/152
1/2+1/14+1/35+1/65+1/104+1/152 = ?
1/2+1/14+1/35+1/65+1/104+1/152= 12/19.
1/2+1/14+1/35+1/65+1/104+1/152
đây là bài tính nhanh , mong các bạn giúp đỡ
1/2+1/14+1/35+1/65+1/104+1/152