Решим уравнение:
a)
\[(3x - 2)^2 - (3x - 4)(3x + 4) = 0\]
Раскроем скобки:
\[(9x^2 - 12x + 4) - (9x^2 - 16) = 0\]
\[9x^2 - 12x + 4 - 9x^2 + 16 = 0\]
\[-12x + 20 = 0\]
\[-12x = -20\]
\[x = \frac{-20}{-12} = \frac{5}{3}\]
б)
\[4y^2 - 81 = 0\]
\[4y^2 = 81\]
\[y^2 = \frac{81}{4}\]
\[y = \pm \sqrt{\frac{81}{4}} = \pm \frac{9}{2}\]
Ответ: а) \(x = \frac{5}{3}\); б) \(y = \pm \frac{9}{2}\)