По теореме Виета:
[tex] {x}^{2} + bx + c = 0\\ x_{1} + x_{2} = - b\\ x_{1} x_{2} = c [/tex]
[tex] {x}^{2} - 5x - 13 = 0 \\ x_{1} + x_{2} = 5 \\ x_{1} x_{2} = - 13 \\ x_{1}x_{2} - 2x_{1} - 2x_{2} = x_{1}x_{2} - 2(x_{1} + x_{2}) = \\ = - 13 - 2 \times 5 = - 13 - 10 = - 23[/tex]
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По теореме Виета:
[tex] {x}^{2} + bx + c = 0\\ x_{1} + x_{2} = - b\\ x_{1} x_{2} = c [/tex]
[tex] {x}^{2} - 5x - 13 = 0 \\ x_{1} + x_{2} = 5 \\ x_{1} x_{2} = - 13 \\ x_{1}x_{2} - 2x_{1} - 2x_{2} = x_{1}x_{2} - 2(x_{1} + x_{2}) = \\ = - 13 - 2 \times 5 = - 13 - 10 = - 23[/tex]