Set $ f'(u) = 0 \Rightarrow 1 - 81u^2 = 0 \Rightarrow u^2 = \frac181 \Rightarrow u = \frac19 $ (since $ u > 0 $). - AMAZONAWS

📅 March 11, 2026 👤 scraface

Mar 11, 2026

$Set $ f'(u) = 0 \Rightarrow 1 - 81u^2 = 0 \Rightarrow u^2 = \frac{1}{81} \Rightarrow u = \frac{1}{9} $ (since $ u > 0 $).$