Question

Daca x + 1/x= 3, x apartine numerelor reale nenule, calculati x la patrat + 1/x la patrat.

Answer 1

 [tex] Ridicam \;la\;patrat\;ambele\;parti\;a\,egalitatii !\\ (x+1/x)^2=3^2\;\Leftrightarrow\;x^2+2*\not{x}*\frac{1}{\not{x}}+\frac{1}{x^2}=9\;\\ x^2+\frac{1}{x^2}=9-2=7[/tex]