\input amstex

$$\aligned
\root 5 \of {1{,}15\cdot1{,}2\cdot1{,}3\cdot1{,}5\cdot1{,}7}&
=\root 5 \of {\frac{115}{100}\cdot\frac{12}{10}\cdot\frac{13}{10}\cdot
\frac{15}{10}\cdot\frac{17}{10}}=\root 5 \of {2^2\cdot3^2\cdot5^2\cdot
13\cdot17\cdot23\cdot\frac{1}{10^6}}=\cr
&=\frac{1}{10}\cdot
\root 5 \of {\frac{1}{10}\cdot2^2\cdot3^2\cdot5^2\cdot13\cdot17\cdot23}%
=\frac{\root 5 \of {2\cdot3^2\cdot5\cdot13\cdot17\cdot23}}{10}
\endaligned$$

\bye