tìm min

E

eye_smile

Ta có: $x^2(x^2+2y^2-3)+(y^2-2)^2=1$

\Leftrightarrow $(x^2+y^2)-4(x^2+y^2)+3=-x^2 \le 0$

\Leftrightarrow $A^2-4A+3 \le 0$ ($A=x^2+y^2$)

\Leftrightarrow $|A-2| \le 1$

\Leftrightarrow $1 \le A \le 3$

\Rightarrow Min A=1 tại $x=0;y=1$
 
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