\(x\cdot x=\frac{2}{18}\)
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\(\frac{x-1}{2013}+\frac{x-2}{2012}+\frac{x-3}{2011}=\frac{x-4}{2010}+\frac{x-5}{2009}+\frac{x-6}{2008}\) ( có lẽ đề như này )
\(\Leftrightarrow\frac{x-1}{2013}-1+\frac{x-2}{2012}-1+\frac{x-3}{2011}-1=\frac{x-4}{2010}-1+\frac{x-5}{2009}-1+\frac{x-6}{2008}-1\)
\(\Leftrightarrow\frac{x-2014}{2013}+\frac{x-2014}{2012}+\frac{x-2014}{2011}-\frac{x-2014}{2010}-\frac{x-2014}{2009}-\frac{x-2014}{2008}=0\)
\(\Leftrightarrow\left(x-2014\right)\left(\frac{1}{2013}+\frac{1}{2012}+\frac{1}{2011}-\frac{1}{2010}-\frac{1}{2009}-\frac{1}{2008}\right)=0\)
\(\Leftrightarrow x-2014=0\left(\frac{1}{2013}+\frac{1}{2012}+\frac{1}{2011}-\frac{1}{2010}-\frac{1}{2009}-\frac{1}{2008}\ne0\right)\)
\(\Leftrightarrow x=2014\)
...
Ta có : \(x^2+9x+20=x^2+4x+5x+20=\left(x+4\right)\left(x+5\right)\)
\(x^2+11x+30=x^2+5x+6x+30=\left(x+5\right)\left(x+6\right)\)
\(x^2+13x+42=x^2+6x+7x+42=\left(x+6\right)\left(x+7\right)\)
\(\Rightarrow Pt\Leftrightarrow\frac{1}{\left(x+4\right)\left(x+5\right)}+\frac{1}{\left(x+5\right)\left(x+6\right)}+\frac{1}{\left(x+6\right)\left(x+7\right)}=\frac{1}{18}\) (*)\(ĐKXĐ:x\ne-4;x\ne-5;x\ne-6;x\ne-7\)
(*) \(\Leftrightarrow\frac{1}{x+4}-\frac{1}{x+5}+\frac{1}{x+5}-\frac{1}{x+6}+\frac{1}{x+6}-\frac{1}{x+7}=\frac{1}{18}\)
\(\Leftrightarrow\frac{1}{x+4}-\frac{1}{x+7}=\frac{1}{18}\)
\(\Leftrightarrow\frac{x+7-x-4}{\left(x+4\right)\left(x+7\right)}=\frac{1}{18}\)
\(\Leftrightarrow3.18=x^2+4x+7x+28\)
\(\Leftrightarrow x^2-2x+13x-26=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+13\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-2=0\\x+13=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\left(tm\right)\\x=-13\left(tm\right)\end{cases}}}\)
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Ta có: \(\frac{6x}{11}=\frac{9y}{2}=\frac{18z}{5}\Leftrightarrow\frac{-18x}{-33}=\frac{18y}{4}=\frac{18z}{5}\)
Áp dụng t/c của dãy tỉ số bằng nhau ta có:
\(\frac{-18x}{-33}=\frac{18y}{4}=\frac{18z}{5}=\frac{18\left(-x+y+z\right)}{-33+4+5}=\frac{18\cdot\left(-120\right)}{-24}=90\)
Do đó:
\(\frac{-18x}{-33}=90\Leftrightarrow x=165\)
\(\frac{18y}{4}=90\Leftrightarrow y=20\)
\(\frac{18z}{5}=90\Leftrightarrow z=25\)
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Xin lỗi nha mk ms lp 6 ak nên ko hỉu.
Bn trả lời câu hỏi bên dưới của mk ik mk k cho!
Ta có : \(\frac{1+2y}{18}=\frac{1+4y}{24}\)
\(\Rightarrow24.\left(1+2y\right)=18.\left(1+4y\right)\)
\(\Rightarrow24+48y=18+72y\)
\(\Rightarrow24-18=72y-48y\)
\(\Rightarrow6=24y\Rightarrow y=\frac{6}{24}=\frac{1}{4}\)
Thay y vào đẳng thức ta có:
\(\frac{1+4.\frac{1}{4}}{24}=\frac{1+6.\frac{1}{4}}{6x}\)
\(\Rightarrow\frac{1}{12}=\frac{5}{2}:6x\)
\(\Rightarrow6x=\frac{5}{2}:\frac{1}{12}=30\)
\(\Rightarrow x=30:6=5\)
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vì x ; x = 2/18
mà x phải bằng nhau nên x bằng
2/18 ; 2 =1/18
\(\times\cdot\times=\frac{1}{9}\)
\(\times\cdot\times=\frac{1}{3}\cdot\frac{1}{3}\)
\(\times=\frac{1}{3}\)
\(xx=\frac{2}{18}=\frac{1}{9}\)
<=> \(x^2=\left(\frac{1}{3}\right)^2\)
<=> \(x=\pm\frac{1}{3}\)
\(x.x=\frac{2}{18}\)
\(x^2=\frac{1}{9}\)
đến đây tịt rùi hc tốt !!!