Tính \(N = \sqrt {\frac{{{{125}^2} - {{100}^2}}}{{400}}} \)

* Hướng dẫn giải

Ta có:

\(\begin{array}{l}
M = \sqrt {\frac{{{{125}^2} - {{100}^2}}}{{400}}} \\
 = \sqrt {\frac{{\left( {125 + 100} \right).\left( {125 - 100} \right)}}{{{{20}^2}}}} \\
 = \sqrt {\frac{{225.25}}{{{{20}^2}}}}  = \frac{{15.5}}{{20}} = \frac{{15}}{4}
\end{array}\)