[tex] a) \frac{ x_{1}+ x_{2} }{ x_{1} x_{2} } = \frac{-7}{-11}= \frac{7}{11} \\ b) x_{1}^2+ x_{2}^2 =( x_{1}+ x_{2})^2-2 x_{1} x_{2}=49+11=60 \\ c)( x_{1} -x_{2})^2= x_{1}^2+ x_{2}^2-2 x_{1} x_{2}=60+11=71 \\ d) \frac{ x_{1}^2+ x_{2}^2 }{ x_{1} x_{2} } = \frac{60}{-11} [/tex]
