\(x.\left(x+1\right)=2+4+6+...+100\)
\(=\left(100+2\right).\left[\left(100-2\right)\div2+1\right]\div2\)
\(=102.\left[98\div2+1\right]\div2\)
\(=102.50\div2\)
\(=2550\)
\(=50.51\)
\(\Rightarrow\hept{\begin{cases}x=50\\x+1=51\end{cases}}\Rightarrow x=50\)
sao bài này lại có trong ngữ văn?