b) Ta có: \(\frac{x+5}{2015}+\frac{x+6}{2014}=\frac{x+7}{2013}+\frac{x+8}{2012}\)
\(\Leftrightarrow\frac{x+5}{2015}+1+\frac{x+6}{2014}+1=\frac{x+7}{2013}+1+\frac{x+8}{2012}+1\)
\(\Leftrightarrow\frac{x+2020}{2015}+\frac{x+2020}{2014}-\frac{x+2020}{2013}-\frac{x+2020}{2012}=0\)
\(\Leftrightarrow\left(x+2020\right)\cdot\left(\frac{1}{2015}+\frac{1}{2014}-\frac{1}{2013}-\frac{1}{2012}\right)=0\)
mà \(\frac{1}{2015}+\frac{1}{2014}-\frac{1}{2013}-\frac{1}{2012}\ne0\)
nên x+2020=0
hay x=-2020
Vậy: x=-2020
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