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22 tháng 10 2017
3(x - 5) - 3(x + 6) = 10 + x
\(\Rightarrow\) 3x - 15 - (3x + 18) = 10 + x
\(\Rightarrow\) 3x - 15 - 3x - 18 = 10 + x
\(\Rightarrow\) -3 = 10 + x
\(\Rightarrow\) x = -13
J
0
TN
29 tháng 4 2017
\(4x-3-x-5-=x+2-2x+2.10\)
\(3x-8=x+2-2x+20\)
\(3x=x+10-2x+20\)
\(3x=-x+30\)
\(4x=30\)
\(x=\frac{30}{4}=7,5\)
18 tháng 6 2016
a) \(\Leftrightarrow\left|2x-3\right|=\frac{1}{4}\Leftrightarrow\orbr{\begin{cases}x\ge\frac{3}{2}\mid:2x-3=\frac{1}{4}\Rightarrow2x=\frac{13}{4}\Rightarrow x=\frac{13}{8}\left(TM\right)\\x< \frac{3}{2}\mid:3-2x=\frac{1}{4}\Rightarrow2x=\frac{11}{4}\Rightarrow x=\frac{11}{8}\left(TM\right)\end{cases}.}\)
b) \(\Leftrightarrow\left|x-1\right|=\frac{3}{4}\Leftrightarrow\orbr{\begin{cases}x\ge1\mid:x-1=\frac{3}{4}\Rightarrow x=\frac{7}{4}\left(TM\right)\\x< 1\mid:1-x=\frac{3}{4}=>x=\frac{1}{4}\left(TM\right)\end{cases}}\)
c) \(\frac{3}{5\left(x-\frac{5}{6}\right)}-\frac{1}{2\left(\frac{3}{2}-1\right)}=-\frac{1}{4}\Leftrightarrow\frac{3}{\frac{5\left(6x-5\right)}{6}}-\frac{1}{2\cdot\frac{1}{2}}=-\frac{1}{4}\Leftrightarrow\frac{18}{5\left(6x-5\right)}=-\frac{1}{4}+1\)
\(\Leftrightarrow\frac{18}{5\left(6x-5\right)}=\frac{3}{4}\Leftrightarrow6x-5=\frac{24}{5}\Leftrightarrow6x=\frac{49}{5}\Leftrightarrow x=\frac{49}{30}\)
d) \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{x\left(x+1\right)}=\frac{2015}{2016}\)
\(\Leftrightarrow\frac{2}{2\cdot3}+\frac{2}{3\cdot4}+\frac{2}{4\cdot5}+...+\frac{2}{x\left(x+1\right)}=\frac{2015}{2016}\)
\(\Leftrightarrow2\cdot\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2015}{2016}\)
\(\Leftrightarrow2\left(\frac{1}{2}-\frac{1}{x+1}\right)=\frac{2015}{2016}\Leftrightarrow2\cdot\frac{x+1-2}{2\left(x+1\right)}=\frac{2015}{2016}\Leftrightarrow\frac{x-1}{x+1}=\frac{2015}{2016}\)
\(\Leftrightarrow2016x-2016=2015x+2015\Leftrightarrow x=2015+2016=4031\)
Vậy x = 4031.
5 tháng 7 2017
\(\dfrac{5}{6}-\dfrac{1}{2}\left(x-\dfrac{1}{3}\right)-\dfrac{2}{5}x=0\Rightarrow\dfrac{1}{2}\left(x-\dfrac{1}{3}\right)-\dfrac{2}{5}x=\dfrac{5}{6}\)
\(\Rightarrow\dfrac{1}{2}x-\dfrac{1}{6}-\dfrac{2}{5}x=\dfrac{5}{6}\Rightarrow\dfrac{1}{2}x-\dfrac{2}{5}x=\dfrac{5}{6}+\dfrac{1}{6}=1\)
\(\Rightarrow x\left(\dfrac{1}{2}-\dfrac{2}{5}\right)=1\Rightarrow\dfrac{1}{10}x=1\Rightarrow x=1:\dfrac{1}{10}=10\)
Vậy x = 10
NT
2
TM
19 tháng 5 2016
Từ \(\frac{x}{2}=\frac{y}{3}=\frac{z}{5}\Rightarrow\frac{x}{2}=\frac{2y}{6}=\frac{z}{5}\)
Theo t/c dãy tỉ số=nhau:
\(\frac{x}{2}=\frac{2y}{6}=\frac{z}{5}=\frac{x-2y+z}{2-6+5}=\frac{10}{1}=10\)
+)x/2=10=>x=20
+)2y/6=10=>2y=60=>y=30
+)z/5=10=>z=50
Vậy................
19 tháng 5 2016
\(\frac{x}{2}=\frac{y}{3}=\frac{z}{5}=\frac{2y}{6}=\frac{x-2y+z}{2-6+5}=10\)
\(\Rightarrow x=20\) \(y=30\) \(z=50\)
\(2(x-5)-3(x+6)=10+x\)
\(\Rightarrow2x-10-3x+18=10x\)
\(\Rightarrow2x-10-3x-18=10+x\)
\(\Rightarrow-x-28=10+x\)
\(\Rightarrow-x-x=10+28\)
\(\Rightarrow-2x=38\)
\(\Rightarrow x=-19\)
Vậy ..
\(2\left(x-5\right)-\left(3x+6\right)=10+x\)
\(\Rightarrow2x-10-3x-18=10+x\)
\(\Rightarrow-x-28=10+x\)
\(\Rightarrow-x=38+x\)
\(\Rightarrow-2x=38\Leftrightarrow x=-19\)