If x - 1/x = 2 √35 then find the value of ( x + 1/x )2

⇒ If x - \(\frac{1}{x}\) = a then x + \(\frac{1}{x}\) = \(\sqrt {a^2 + 4}\)

Here,

x - \(\frac{1}{x}\) = 2\(\sqrt{35}\), then 

⇒ x + \(\frac{1}{x}\) = \(\sqrt {(2\sqrt{35})^2 + 4}\) = 12

⇒ ( x + \(\frac{1}{x}\) )² = 12² = 144