Найдите значение выражения: (x^2-25)/(9x^2+6xy+4y^2):(x^2+5x)/(27x^3-8y^3) при x=25; y=12,5.

\[\frac{x^{2} - 25}{9x^{2} + 6xy + 4y^{2}}\ :\frac{x^{2} + 5x}{27x^{3} - 8y^{3}} =\]

\[= \frac{(x - 5)(x + 5)\left( 27x^{3} - 8y^{3} \right)}{\left( 9x^{2} + 6xy + 4y^{2} \right) \cdot x(x + 5)} =\]

\[= \frac{(x - 5)(3x - 2y)\left( 9x^{2} - 6xy + 4y^{2} \right)}{x\left( 9x^{2} + 6xy + 4y^{2} \right)} =\]

\[= \frac{(x - 5)(3x - 2y)}{x};\]

\[x = 25;\ \ y = 12,5:\]

\[\frac{(25 - 5)(3 \cdot 25 - 2 \cdot 12,5)}{25} =\]

\[= \frac{20 \cdot 50}{25} = 20 \cdot 2 = 40.\]