21 tháng 10 lúc 23:33
cứu em với ạ
\(...=\left(x+\sqrt{x^2+2015}\right)\left(x-\sqrt{x^2+2015}\right)\left(y+\sqrt{y^2+2015}\right)=2015\left(x-\sqrt{x^2+2015}\right)\)
\(\Leftrightarrow-2015\left(y+\sqrt{y^2+2015}\right)=2015\left(x-\sqrt{x^2+2015}\right)\)
\(\Leftrightarrow-y-\sqrt{y^2+2015}=x-\sqrt{x^2+2015}\left(1\right)\)
Tương tự ta được :
\(-x-\sqrt{x^2+2015}=y-\sqrt{y^2+2015}\left(2\right)\)
\(\left(1\right)+\left(2\right)\Rightarrow2\left(x+y\right)=0\)
\(\Leftrightarrow x+y=0\)
\(\Rightarrow A=x+y+2016=2016\)
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