If (3 + 2 sqrt 5 )2 = 29 + K sqrt 5 Find value of K2

Formula → (a + b)² = a² + b² + 2ab

Given, (3 + 2\(\sqrt {5}\))² = 29 + K\(\sqrt {5}\)

⇒ 9 + 20 + 12\(\sqrt {5}\) = 29 + K\(\sqrt {5}\)

29 + 12\(\sqrt {5}\) = 29 + K\(\sqrt {5}\)            [compare coefficients]

K = 12

K² = 144