\[25x - x^{3} = 0\]
\[- x\left( x^{2} - 25 \right) = 0\]
\[- x(x + 5)(x - 5) = 0\]
\[x = 0;x = - 5;\ \ x = 5.\]
\[Ответ:x = 5 - наибольший.\]