x1+x2=1/3; x1x2=-2/3
\(P=\dfrac{x_1^3-x_2^3}{x_1x_2}=\dfrac{\left(x_1-x_2\right)\left(x_1^2+x_2^2+x_1x_2\right)}{x_1x_2}\)
\(=\dfrac{\left(x_1-x_2\right)\cdot\left[\left(x_1+x_2\right)^2-x_1x_2\right]}{-\dfrac{2}{3}}=\dfrac{\left(x_1-x_2\right)\cdot\dfrac{7}{9}}{-\dfrac{2}{3}}\)
\(=\left(x_1-x_2\right)\cdot\dfrac{-7}{6}\)
(x1-x2)^2=(x1+x2)^2-4x1x2=(1/3)^2-4*(-2/3)=1/9+8/3=1/9+24/9=25/9
=>x1-x2=5/3 hoặc x1-x2=-5/3
=>P=-35/18 hoặc P=35/18
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