tìm số tự nhiên x biết
1/5.8+1/8.11+.....=1/x.(x+1)=1/18
Tìm số tự nhiên x biết : \(\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{x.\left(x+3\right)}=\frac{1}{18}\)
\(\frac{1}{5.8}+\frac{1}{8.11}+..+\frac{1}{x.\left(x+3\right)}=\frac{1}{18}\)
\(\frac{1}{3}.\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{1}{18}\)
\(\frac{1}{5}-\frac{1}{x+3}=\frac{1}{18}:\frac{1}{3}\)
\(\frac{1}{5}-\frac{1}{x+3}=\frac{1}{6}\)
\(\frac{1}{x+3}=\frac{1}{30}\)
\(x+3=30\)
\(x=27\)
Vậy x=27
\(\Leftrightarrow\frac{3}{5\cdot8}+\frac{3}{8\cdot11}+..+\frac{3}{x\left(x+3\right)}=\frac{3}{18}\)
\(\Leftrightarrow\frac{8-5}{5\cdot8}+\frac{11-8}{8\cdot11}+...+\frac{x+3-x}{x\left(x+3\right)}=\frac{1}{6}\)
\(\Leftrightarrow\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{x}-\frac{1}{x+3}=\frac{1}{6}\)
\(\Leftrightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{1}{6}\Leftrightarrow\frac{1}{x+3}=\frac{1}{5}-\frac{1}{6}=\frac{1}{30}\Leftrightarrow x+3=30\Leftrightarrow x=27\)
Vậy số tự nhiên x là 27.
1/5.8 + 1/8.11 + ... + 1/x.(x+3) = 1/18
3/5.8 + 3/8.11 + ... + 3/x.(x+3) = 3.1/18
1/5 - 1/8 + 1/8 - 1/11 + ... + 1/x - 1/x+3 = 1/6
1/5 - 1/x+3 = 1/6
1/x+3 = 1/5 - 1/6
1/x+3 = 6/30 - 5/30 = 1/30
=> x+3 = 30
=> x = 27
Vậy x = 27
Tìm x biết :
1/5.8+ 1/8.11+ 1/11.14+...+1/x.(x+3)= 101/1540
Tìm x biết:
1/5.8+1/8.11+1/11.14+......+1/x(x+3)=98/1545
tìm x biết 1/5.8+1/8.11+1/11.14+..............+1/x[x+3]=101/1540
\(\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+...+\frac{1}{x\left(x+3\right)}=\frac{101}{1540}\)
\(\Rightarrow\frac{1}{3}\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+...+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{101}{1540}\)
\(\Rightarrow\frac{1}{3}\left(\frac{1}{5}-\frac{1}{x+3}\right)=\frac{101}{1540}\)
\(\Rightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{101}{1540}:\frac{1}{3}\)
\(\Rightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{303}{1540}\)
\(\Rightarrow\frac{1}{x+3}=\frac{1}{5}-\frac{303}{1540}\)
=> \(\frac{1}{x+3}=\frac{1}{308}\)
=> x + 3 = 308
=> x = 308 - 3
=> x = 305
Tìm x biết: (1/2.5+1/5.8+1/8.11+...+1/65.68)x-7/34=19/68
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Tìm x , biết : \(\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+...+\frac{1}{x.(x+3)}=\frac{101}{1504} \)
Câu hỏi của Nguyễn Ánh Ngân - Toán lớp 6 - Học toán với OnlineMath
Bạn tham khảo
\(\frac{1}{5\cdot8}+\frac{1}{8\cdot11}+\frac{1}{11\cdot14}+...+\frac{1}{x\cdot\left(x+3\right)}=\frac{101}{1504}\)
\(\Rightarrow\frac{1}{3}\cdot\left(\frac{3}{5\cdot8}+\frac{3}{8\cdot11}+\frac{3}{11\cdot14}+...+\frac{3}{x\cdot\left(x+3\right)}\right)=\frac{101}{1504}\)
\(\Rightarrow\frac{1}{3}\cdot\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+...+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{101}{1504}\)
\(\Rightarrow\frac{1}{3}\cdot\left(\frac{1}{5}-\frac{1}{x+3}\right)=\frac{101}{1504}\Rightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{101}{1504}:\frac{1}{3}\)
\(\Rightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{101}{1504}\cdot\frac{3}{1}=\frac{303}{1504}\)
- Đến đây tự tính nhé :v
#Amano Ichigo:
- Bn ơi kq của biểu thức tìm x phải bằng \(\frac{101}{1540}\) mới đúng nhé =)
Học tốt !! :v
Tìm x 1/5.8+1/8.11+1/11.14+...+1/x.(x+3)=98/1545
Tìm x biết:
3.x/2.5+3.x/5.8+3.x/8.11+3.x/11.14=1/21
trả lời hộ mik mik cho 1 link
tìm x biết
1/5.8+1/8.11+1/11.14+...+1/x(x+3)=101/15401+1/3+1/6+1/10+...+1/x(x+1):2=1 1991/1993