a)-3x+11=14
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\(\dfrac{3x}{2\cdot5}+\dfrac{3x}{5\cdot8}+\dfrac{3x}{8\cdot11}+\dfrac{3x}{11\cdot14}=\dfrac{1}{21}\\ x\cdot\left(\dfrac{3}{2\cdot5}+\dfrac{3}{5\cdot8}+\dfrac{3}{8\cdot11}+\dfrac{3}{11\cdot14}\right)=\dfrac{1}{21}\\ x\cdot\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}\right)=\dfrac{1}{21}\\ x\cdot\left(\dfrac{1}{2}-\dfrac{1}{14}\right)=\dfrac{1}{21}\\ x\cdot\dfrac{3}{7}=\dfrac{1}{21}\\ x=\dfrac{1}{21}:\dfrac{3}{7}\\ x=\dfrac{1}{9}\)
\(\frac{3x}{2.5}+\frac{3x}{5.8}+\frac{3x}{8.11}+\frac{3x}{11.14}=\frac{1}{21}\)
\(3x.\left(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}\right)=\frac{1}{21}\)
\(3x.\frac{1}{7}=\frac{1}{21}\)
\(\frac{3}{7}x=\frac{1}{21}\)
\(x=\frac{1}{21}:\frac{3}{7}\)
\(x=\frac{7}{81}\)
\(\frac{3x}{2\cdot5}+\frac{3x}{5\cdot8}+\frac{3x}{8\cdot11}+\frac{3x}{11\cdot14}=\frac{1}{21}\)
\(=>\frac{3x}{3}\left[\frac{3}{2\cdot5}+\frac{3}{5\cdot8}+\frac{3}{8\cdot11}+\frac{3}{11\cdot14}\right]=\frac{1}{21}\)
\(=>x\left[\frac{3}{2\cdot5}+\frac{3}{5\cdot8}+\frac{3}{8\cdot11}+\frac{3}{11\cdot14}\right]=\frac{1}{21}\)
\(=>x\left[\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{11}-\frac{1}{14}\right]=\frac{1}{21}\)
\(=>x\left[\frac{1}{2}-\frac{1}{14}\right]=\frac{1}{21}\)
\(=>x\cdot\frac{3}{7}=\frac{1}{21}\Leftrightarrow x=\frac{1}{9}\)
\(\frac{3x}{2.5}+\frac{3x}{5.8}+\frac{3x}{8.11}+\frac{3x}{11.14}=\frac{1}{21}\)
=> \(x\left(\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+\frac{3}{11.14}\right)=\frac{1}{21}\)
=> \(x\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}\right)=\frac{1}{21}\)
=> \(x\left(\frac{1}{2}-\frac{1}{14}\right)=\frac{1}{21}\)
=> \(x.\frac{3}{7}=21\)
=> x = 49
Vậy x = 49
https://olm.vn/hoi-dap/tim-kiem?q=T%C3%ACm+x,+bi%E1%BA%BFt:+3x2.5++3x5.8++3x8.11++3x11.14+=121+&id=81551
Cậu vào link này nhé(đây là đáp án câu này)
a) 2|5x - 3| - 2x = 14
=> 2|5x - 3| = 14 + 2x
=> |5x - 3| = x + 7
=> \(\orbr{\begin{cases}5x-3=x+7\\5x-3=-x-7\end{cases}}\)
=> \(\orbr{\begin{cases}5x-x=7+3\\5x+x=-7+3\end{cases}}\)
=> \(\orbr{\begin{cases}4x=10\\6x=-4\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{5}{2}\\x=-\frac{2}{3}\end{cases}}\)(tm)
a,x-11 là bội của x+2
=>x+2-13 chia hết cho x+2
=>13 chia hết cho x+2
=>x+2\(\in\)Ư(13)={-13,-1,1,13}
=>x\(\in\){-15,-3,-1,11}
b,x-11 là ước của 3x+14
=>3x-33+47 chia hết cho x-11
=>3(x-11)+47 chia hết cho x-11
=>47 chia hết cho x-11
=>x-11\(\in\)Ư(47)={-47,-1,1,47}
=>x\(\in\){-36,10,12,58}
a) \(12+x+\left(-5\right)=-18-2x\)
\(\Rightarrow12+x-5=-18-2x\)
\(\Rightarrow x+7+18+2x=0\)
\(\Rightarrow3x=-25\)
\(\Rightarrow x=-\dfrac{25}{3}\)
b) \(\left(-14\right)-x+\left(-15\right)=-10+\left(4-2x\right)\)
\(\Rightarrow-14-x-15=-10+4-2x\)
\(\Rightarrow-x-29=-2x-6\)
\(\Rightarrow-x+2x=-6+29\)
\(\Rightarrow x=23\)
c) \(x-\left(-19\right)-\left(-11\right)=-\left(3x+40\right)\)
\(\Rightarrow x+19+11=-3x-40\)
\(\Rightarrow x+30=-3x-40\)
\(\Rightarrow x+3x=-40-30\)
\(\Rightarrow4x=-70\)
\(\Rightarrow x=-\dfrac{35}{2}\)
\(\left(\frac{1}{2}+\frac{3}{5}-\frac{2}{15}\right):\frac{3}{5}\)
\(\left(\frac{15}{30}+\frac{18}{30}-\frac{4}{30}\right).\frac{5}{3}\)
\(\frac{29}{30}.\frac{5}{3}=\frac{29}{18}\)
\(-3x+11=14\)
\(-3x=14-11\)
\(-3x=3\)
\(x=-1\)
- 3X + 11 = 14
-3X = 14 - 11
-3X = 3
x = -1