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log in baza 3 din ( x^2-1) = 2 + log in baza 3 din ( x-1 )

Răspuns :

DVA:x>1
[tex] log_{3}( x^{2}-1)= log_{3}9+ log_{3}(x-1) [/tex]
[tex] log_{3}( x^{2} -1)= log_{3}9(x-1) [/tex]
[tex] x^{2} -1=9(x-1)[/tex]
[tex] x^{2} -9x+8=0[/tex]
Δ=81-32=49
[tex] x_{1} = \frac{9-7}{2}=1 [/tex]
[tex] x_{2}= \frac{9+7}{2}=8 [/tex]
Raspuns:{8}