Giải thích các bước giải:
\(\begin{array}{l}
VT = \frac{{15}}{{26}} + \frac{{10}}{{17}} + \frac{8}{{21}}\\
= \frac{{15.17.21 + 10.26.21 + 8.10.15}}{{26.17.21}}\\
= \frac{{5355 + 5460 + 1200}}{{9282}} = \frac{{12015}}{{9282}}\\
= \frac{{9282 + 2733}}{{9282}}\\
= 1 + \frac{{2733}}{{9282}} < 1 + 1 = VP\left( {do:\frac{{2733}}{{9282}} < 1} \right)\\
\to dpcm
\end{array}\)