Relax

Respuesta :

[tex]\left(x-\dfrac{1}{x}\right)^2=\\ x^2-2+\dfrac{1}{x^2}=\\ x^2+2+\dfrac{1}{x^2}-4=\\ \left(x+\dfrac{1}{x}\right)^2-4=\\ 4^2-4=16-4=12 [/tex]