[Bat dang thuc]

F

fuck_you_98

2.a^2-2ab+2b^2-4b+7<0
=2a^2-4ab+4b^2-8a+14<0
=(a-b)^2+(a-4)^2-2<0
do (a-b)^2>=0;(a-4)^2>=0;-2<0
suy ra a=b=4
 
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