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Rezolvati in multimea numerelor reale ecuatia :√x+1-√x-1=√2


Răspuns :

[tex] \sqrt{x+1}- \sqrt{x-1} = \sqrt{2}\\ [/tex]

Conditiile de existanta a radicalilor:
x + 1 ≥ 0  ==>  x ∈ [-1, ∞)
x - 1 ≥ 0  ==>  x ∈ [1, ∞)

Intersectia: x ∈ [1, ∞)

Ridicam la patrat ecuatia:

[tex](x+1)-2 \sqrt{(x+1)(x-1)}+(x-1)=2 \\ 2x-2 \sqrt{x^2-1}=2\\ \sqrt{x^2-1}=x-1 [/tex]

Ridicam din nou la patrat:

[tex]x^2-1=x^2-2x+1\\ 2x=2\\ x=1[/tex]