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Found problems: 1

Let be a sequence of functions $ \left( f_n \right)_{n\ge 2}:\mathbb{R}_{\ge 0}\longrightarrow\mathbb{R} $ defined, for each $ n\ge 2, $ as $$ f_n(x)=2nx^{2+n} -2(n+2)x^{1+n} +(2+n)x +1. $$ [b]a)[/b] Prove that $ f_n $ has an unique local maxima $ x_n, $ for any $ n\ge 2. $ [b]b)[/b] Show that $ 1=\lim_{n\to\infty } x_n. $ [i]Cătălin Zîrnă[/i]