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Question-150697




Question Number 150697 by mathdanisur last updated on 14/Aug/21
Answered by dumitrel last updated on 14/Aug/21
1011≤a_i ≤2022  (1/(2022))≤(1/b_i )≤(1/(1011))⇒  (1/2)≤(a_i /b_i )≤2⇒((a_i /b_i )−(1/2))((a_i /b_i )−2)≤0⇒a_i ^2 +b_i ^2 ≤(5/2)a_i b_i ⇒  Σa_i ^2 +Σb_i ^2 ≤(5/2)Σa_i b_i
$$\mathrm{1011}\leqslant{a}_{{i}} \leqslant\mathrm{2022} \\ $$$$\frac{\mathrm{1}}{\mathrm{2022}}\leqslant\frac{\mathrm{1}}{{b}_{{i}} }\leqslant\frac{\mathrm{1}}{\mathrm{1011}}\Rightarrow \\ $$$$\frac{\mathrm{1}}{\mathrm{2}}\leqslant\frac{{a}_{{i}} }{{b}_{{i}} }\leqslant\mathrm{2}\Rightarrow\left(\frac{{a}_{{i}} }{{b}_{{i}} }−\frac{\mathrm{1}}{\mathrm{2}}\right)\left(\frac{{a}_{{i}} }{{b}_{{i}} }−\mathrm{2}\right)\leqslant\mathrm{0}\Rightarrow{a}_{{i}} ^{\mathrm{2}} +{b}_{{i}} ^{\mathrm{2}} \leqslant\frac{\mathrm{5}}{\mathrm{2}}{a}_{{i}} {b}_{{i}} \Rightarrow \\ $$$$\Sigma{a}_{{i}} ^{\mathrm{2}} +\Sigma{b}_{{i}} ^{\mathrm{2}} \leqslant\frac{\mathrm{5}}{\mathrm{2}}\Sigma{a}_{{i}} {b}_{{i}} \\ $$
Commented by mathdanisur last updated on 14/Aug/21
Cool Ser, thank you
$$\mathrm{Cool}\:\boldsymbol{\mathrm{S}}\mathrm{er},\:\mathrm{thank}\:\mathrm{you} \\ $$

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