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Daca x € lui R*,astfel incat x+1 supra x=4,atunci aflati valoarea sumei x patrat plus unu supra x patrat

Răspuns :

[tex] \frac{x+1}{x}=4 [/tex]
x+1 = 4x
[tex] \frac{ x^{2}+1}{ x^{2}} [/tex]
[tex] \frac{(x-1)(x+1)}{ x^{2} } = \frac{(x-1)* 4x}{ x^{2}} = \frac{ 4x^{2}-4x}{ x^{2} } [/tex]
simplifici pe [tex] x^{2} [/tex] si rezultatul e 4-4x

x+1/x=4
(x+1/x)²=4²
x²+2×x×1/x+1/x²=16
x²+2+1/x²=16 =>
x²+1/x²=14