1, Cho x; y; z ≠0 và \(\dfrac{1}{x}\) + \(\dfrac{1}{y}\)+ \(\dfrac{1}{z}\)=\(\dfrac{2}{2x+y+2z}\). Cmr: (2x+y)(y+2z)(z+x)= 0
2, Cho \(\dfrac{a}{b+c}+\dfrac{b}{c+a}+\dfrac{c}{a+b}=1\). Cmr: \(\dfrac{a^2}{b+c}+\dfrac{b^2}{c+a}+\dfrac{c^2}{a+b}=0\)
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