\(\frac{x+2}{11}+\frac{x+2}{12}+\frac{x+2}{13}=\frac{x+2}{14}+\frac{x+2}{15}\)
\(\Leftrightarrow\frac{x+2}{11}+\frac{x+2}{12}+\frac{x+2}{13}-\frac{x+2}{14}-\frac{x+2}{15}=0\)
\(\Leftrightarrow\left(x+2\right)\left(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}-\frac{1}{14}-\frac{1}{15}\right)=0\)
\(\Leftrightarrow x+2=0\). Do \(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}-\frac{1}{14}-\frac{1}{15}\ne0\)
\(\Leftrightarrow x=-2\)
x+2/11+x+2/12+x+2/13=x+2/14+x+2/15
(x+x+x)+(2/11+2/12+2/13)= (x+x)+(2/14+2/15)
x.3+431/858 = x.2 + 29/105
x.3-x.2=-431/858 +29/105
x.1 =-6791/30030
x= -9791/30030:1
x= -9791/30030
vậy x= -9791/ 30030
