488 2) 5x2-5y² 3x²+3y² при х = =, у =;

2) Вычислить значение выражения при х = 5/6, у = 2/3.

$$ \frac{5x^2-5y^2}{3x^2+3y^2} = \frac{5(x^2-y^2)}{3(x^2+y^2)} = \frac{5((\frac{5}{6})^2-(\frac{2}{3})^2)}{3((\frac{5}{6})^2+(\frac{2}{3})^2)} = \frac{5(\frac{25}{36}-\frac{4}{9})}{3(\frac{25}{36}+\frac{4}{9})} = \frac{5(\frac{25}{36}-\frac{16}{36})}{3(\frac{25}{36}+ \frac{16}{36})} = \frac{5 \cdot \frac{9}{36}}{3 \cdot \frac{41}{36}} = \frac{5 \cdot 9}{3 \cdot 41} = \frac{5 \cdot 3}{41} = \frac{15}{41} $$

Ответ: $$ \frac{15}{41} $$