Ответ:

x₁·y₁ + x₂·y₂ = 0

Объяснение:

[tex]\left \{ \begin{array}{l} 2x^2 + y = 7 ~\big |\cdot 3 \\\\ 5x^2 + 3y = 17 \end{array}\right. \\\\\\ \ominus \left \{ \begin{array}{l} 6x^2 + 3y = 21 \\\\ \underline{5x^2 + 3y = 17} \end{array}\right. \\\\\\~\hspace{3em} x^2 = 4 \\\\ ~\hspace{3em} x _{1,2} = \pm 2[/tex]

[tex]y_ 1= 7-2x^2 = - 1 \\\\ y _2 = 7 - 2x^2 = -1[/tex]

[tex]\boldsymbol{x_1 y_1 + x_2 y _2 = 2\cdot (-1 )+ (-2)\cdot (-1) = -2 + 2= 0 }[/tex]