X * 3/4 + */5 +1.05 * x =5.8
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Z
5
6 tháng 9 2020
a) 2/2.5 + 2/5.8 + 2/8.11 + ... + 2/x(x+3) = 7/23
3/2.5 + 3/5.8 + 3/8.11 + ... + 3/x(x+3) = 21/46
1/2 - 1/5 + 1/5 - 1/8 + 1/8 - 1/11 + ... + 1/x - 1/x+1 = 21/46
1/2 - 1/x+1 = 21/46
=> 1/x+1 = 1/23
=> x + 1 = 23
=> x = 22
Vậy x = 22.
b) 3/4 . x - 1/5 = 7/4 . x + 11/5
3/4 . x - 7/4 . x = 1/5 + 11/5
x (3/4 - 7/4) = 12/5
-x = 12/5
x = -12/5
Vậy x = -12/5.
TH
3
29 tháng 7 2018
\(\frac{4}{2\cdot5}+\frac{4}{5\cdot8}+...+\frac{4}{x\cdot\left(x+3\right)}=\frac{22}{35}\)
\(\frac{3}{2\cdot5}+\frac{3}{5\cdot8}+...+\frac{3}{x\cdot\left(x+3\right)}=\frac{33}{70}\)
\(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{x}-\frac{1}{x+3}=\frac{33}{70}\)
\(\frac{1}{2}-\frac{1}{x+3}=\frac{33}{70}\)
\(\frac{1}{x+3}=\frac{1}{35}\)
\(\Rightarrow x+3=35\)
\(\Rightarrow x=32\)
29 tháng 7 2018
\(\frac{4}{2\cdot5}+\frac{4}{5\cdot8}+...+\frac{4}{x\left(x+3\right)}=\frac{22}{35}\)
\(\frac{3}{4}\left(\frac{4}{2\cdot5}+\frac{4}{5\cdot8}+...+\frac{4}{x\left(x+3\right)}\right)=\frac{3}{4}\cdot\frac{22}{35}\)
\(\frac{3}{2\cdot5}+\frac{3}{5\cdot8}+...+\frac{3}{x\left(x+3\right)}=\frac{33}{70}\)
\(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{x}-\frac{1}{x+3}=\frac{33}{70}\)
\(\frac{1}{2}-\frac{1}{x+3}=\frac{33}{70}\)
\(\frac{1}{x+3}=\frac{1}{35}\)
\(\Rightarrow x+3=35\)
\(\Rightarrow x=32\)
Vậy x=32
8 tháng 3 2020
\(\text{-7129+1478+7129+(-1479)}\)
\(=\text{-7129+7129+1478+(-1479)}\)
\(=0-1=-1\)
8 tháng 3 2020
\(\text{|-5|.(-7)+4.(-9)}\)
\(=\text{5.(-7)+4.(-9)}\)
\(=\left(-35\right)+\left(-36\right)=-71\)
VD
3 tháng 4 2018
x.\(\left(\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+\frac{3}{11.14}+\frac{3}{14.17}\right)=-1\frac{3}{5}\)
x.\(\left(\frac{5-2}{2.5}+\frac{8-5}{5.8}+\frac{11-8}{8.11}+\frac{14-11}{11.14}+\frac{17-14}{14.17}\right)=\frac{-8}{5}\)
x.\(\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{17}\right)=\frac{-8}{5}\)
x.\(\left(\frac{1}{2}-\frac{1}{17}\right)=\frac{-8}{5}\)
x.\(\left(\frac{17}{34}-\frac{2}{34}\right)=\frac{-8}{5}\)
x.\(\frac{15}{34}=\frac{-8}{5}\)
x\(=\frac{-8}{5}:\frac{15}{34}\)
x\(=\frac{-8}{5}.\frac{34}{15}\)
x\(=\frac{-272}{75}\)
Vậy x\(=\frac{-272}{75}\)
14 tháng 4 2019
\(\left(x-3\right)^2+\frac{-9}{25}=\frac{2}{5}.\frac{8}{5}\)
\(\left(x-3\right)^2+\frac{-9}{25}=\frac{16}{25}\)
\(\left(x-3\right)^2=\frac{16}{25}+\frac{-9}{25}\)
\(\left(x-3\right)^2=\frac{7}{25}\)
\(\left(x-3\right)^2=\left(\frac{7}{5}\right)^2\)
\(\Rightarrow x-3=\frac{7}{5}\)
\(\Rightarrow x=\frac{7}{5}+3\)
\(\Rightarrow x=\frac{22}{5}\)