Partea intreaga a unui numar este:
cel mai mare intreg nai mic decat numarul dat.
[tex]\displaystyle\\
n\times n\ \textless \ n(n+1) \ \textless \ (n+1)(n+1)\\\\
\sqrt{n\times n} \ \textless \ \sqrt{n(n+1)}\ \textless \ \sqrt{(n+1)(n+1)}\\\\
n \ \textless \ \sqrt{n(n+1)}\ \textless \ n+1\\\\
\Longrightarrow~~ \left[\sqrt{n(n+1)}\right]=n\\\\
\Longrightarrow [\sqrt{1*2}]+ [\sqrt{2*3}]+...+ [ \sqrt{50*51}]=1+2+\cdots+50 \\\\
1+2+\cdots+50 = \frac{50\times 51}{2}=25\times 51=\boxed{\bf 1275}[/tex]