Min max

V

vuongchomo

C

conga222222

$\eqalign{
& dk: - {1 \over 2} \le a,b \cr
& \to a + b \ge - 1\;\left( {nhung\;dau\; = \;ko\;xay\;ra\;duoc \to a + b > - 1} \right) \cr
& {\left( {a + b} \right)^2} = {a^2} + {b^2} + 2ab \ge 1 \to a + b \ge 1\;\left( {do\;a + b > - 1} \right) \cr
& \to {P^2} = 2 + 2\left( {a + b} \right) + 2\sqrt {1 + 2\left( {a + b} \right) + 4ab} \ge 2 + 2*1 + 2\sqrt {1 + 2*1 + 4*0} = 4 + 2\sqrt 3 = {\left( {\sqrt 3 + 1} \right)^2} \cr
& \to P \ge \sqrt 3 + 1 \cr
& dau = \leftrightarrow ... \cr
& con\;max\;thi\;cosi\;hay\;bunhiacopski\;binh\;thuong\;chac\;e\;lam\;duoc\;roi\;nen\;thoi\;tu\;lam\;nhe\;:) \cr} $
 
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