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Calculati x pătrat+1/x patrat stiind ca. x-1/x=3 Va rog am nevoie urgent !!!

Răspuns :

[tex]x-\dfrac{1}{x}=3 \Rightarrow \left(x-\dfrac{1}{x}\right)^2=3^2 \Rightarrow x^2-2\cdot x\cdot\dfrac{1}{x} +\left(\dfrac{1}{x}\right)^2 =9 \\\;\\ \Rightarrow x^2-2+\dfrac{1}{x^2}=9 \ \Rightarrow \ x^2+\dfrac{1}{x^2} =9+2 \ \Rightarrow \ x^2+\dfrac{1}{x^2} = 11 \\ .[/tex]