[tex]\displaystyle\bf\\x^{2} +5x-10=0\\\\Teorema \ Vieta \ :\\\\x_{1} + x_{2} =-5\\\\x_{1} \cdot x_{2} =-10\\\\\\(x_{1} + x_{2})^{2} \cdot(x_{1}\cdot x_{2} )=(-5)^{2} \cdot (-10)=25\cdot(-10)=-250[/tex]