x + x +1 phan 2 + x + 8 phan 10 = 136 .Tim x
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\(\frac{1}{6}=\frac{x}{18}\Rightarrow x=3\)
\(\frac{x}{8}=-\frac{1}{4}\Rightarrow x=-2\)
\(\frac{4}{-5}=\frac{x}{10}\Rightarrow x=-8\)
\(\frac{11}{5}=-\frac{22}{x}\Rightarrow x=-10\)
\(\frac{x}{8}=\frac{8}{x}\Rightarrow x^2=64\Rightarrow x=8\)
\(\frac{x}{-11}=-\frac{11}{x}\Rightarrow x^2=121\Rightarrow x=11\)
#H
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\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+....+\frac{1}{x\left(x+1\right)}=\frac{2008}{2009}\)
\(=>\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{x\left(x+1\right)}=\frac{2008}{2009}\)
\(=>\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{2008}{2009}\)
\(=>1-\frac{1}{x+1}=\frac{2008}{2009}=>\frac{1}{x+1}=1-\frac{2008}{2009}=\frac{1}{2009}\)
=>x+1=2009
=>x=2008
Vậy x=2008
1/2+1/6+1/12+...+1/x*(x+1)=2008/2009
1/1*2+1/2*3+1/3*4+...+1/x*(x+1)=2008/2009
1-1/2+1/2-1/3+1/3-1/4+...+1/x-1/(x+1)=2008/2009
1-1/x+1)=2008/2009
1/x+1=1-2008/2009
1/x+1=1/2009
nên x+1=2009
x=2009-1
x=2008 (tick nha)
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\(\frac{x+1}{-2}=-\frac{8}{x+1}\)
\(\Rightarrow\left(x+1\right)\left(x+1\right)=-8.-2\)
\(\Rightarrow\left(x+1\right)^2=16\)
\(\Rightarrow\orbr{\begin{cases}x+1=4\\x+1=-4\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=3\\x=-5\end{cases}}\)
Vậy \(\orbr{\begin{cases}x=3\\x=-5\end{cases}}\)
Dấu \(\orbr{\begin{cases}\\\end{cases}}\)là dấu hoặc nhé !!!
Chúc bạn học tốt !!!