👤

Calculati [tex] x^{2} [/tex] + [tex] \frac{1} x^{2} [/tex] , stiind că [tex]x + \frac{1}{x} = 3 [/tex] unde x ∈ [tex]R ^{*} [/tex]

Răspuns :

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