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Stiind ca x+1/x=3 , x inclus R* calculati x la a doua +1/x la a doua. Raspunsul este?

Răspuns :

[tex]x+ \frac{1}{x}=3 \\ (x+ \frac{1}{x})^{2}=x^2+ \frac{1}{x^2}+2*x* \frac{1}{x} \\ 9=x^2+ \frac{1}{x^2}+2 \\ x^2+ \frac{1}{x^2}=7[/tex]