4. Разложите на множители многочлен: а) \(9ax-12ay\); б) \(\frac{9}{49}x^4-\frac{4}{25}y^4\).

1. \(9ax-12ay=3a(3x-4y)\).
2. \[\frac{9}{49}x^4-\frac{4}{25}y^4=\left(\frac{3x^2}{7}\right)^2-\left(\frac{2y^2}{5}\right)^2=\left(\frac{3x^2}{7}-\frac{2y^2}{5}\right)\left(\frac{3x^2}{7}+\frac{2y^2}{5}\right).\]

Ответ: а) \(3a(3x-4y)\); б) \(\left(\frac{3x^2}{7}-\frac{2y^2}{5}\right)\left(\frac{3x^2}{7}+\frac{2y^2}{5}\right)\).