[tex] {x}^{2} + 10x - 4 = 0 \\ x_{1} + x _{2} = - 10 \\ x_{1} \times x _{2} = - 4 \\ (x_{1} + x _{2}) {}^{2} = x {}^{2} _{1} + 2x_{1} x _{2} + x {}^{2} _{2} \\ x {}^{2} _{1} + x {}^{2} _{2} = x {}^{2} _{1} + 2x_{1} x _{2} + x {}^{2} _{2} - 2 x_{1} x _{2} = \\ ( x_{1} + x _{2} ) {}^{2} - 2 x_{1} x _{2} = \\ ( - 10) {}^{2} - 2 \times ( -4 ) = 100 + 8 = 108[/tex]