2018+.....+(x+1)+x=\(\dfrac{\left(2018+x\right)\left(2018-x+1\right)}{2}=2018\)
\(\Leftrightarrow\left(2018+x\right)\left(2019-x\right)=4036\)
\(\Leftrightarrow2018.2019+x-x^2=2018.2\)
\(\Leftrightarrow2018.2017+x-x^2=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2018\left(l\right)\\x=-2017\left(nh\right)\end{matrix}\right.\)
vậy x=-2017