Số số hạng
\(\left(x-1\right):1+1=x\)
Tổng
\(\left(x+1\right)\cdot x:2=500500\) \(\left(x\ge0\right)\)
\(\left(x+1\right)x=500500\cdot2\)
\(x^2+x=1001000\)
\(x^2+x-1001000=0\)
\(\orbr{\begin{cases}x=1000\left(n\right)\\x=-1001\left(l\right)\end{cases}}\)
\(x=1000\)
Ta có: \(1+2+3+...+x=500500\)
\(\Leftrightarrow\frac{x\left(x+1\right)}{2}=500500\)
\(\Leftrightarrow x^2+x-1001000=0\)
\(\Leftrightarrow\left(x-1000\right)\left(x+1001\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x=1000\left(tm\right)\\x=-1001\left(ktm\right)\end{cases}}\)
