Ответ: 1

[tex]x(x + 14) - (x - 7)^{2} = {x}^{2} + 14x - {x}^{2} + 14x - 49 = 28x - 49[/tex]

При х равно 1 11/14 будет

[tex]28 \times 1 \frac{11}{14} - 49 = 28 \times \frac{25}{14} - 49 = 50 - 49 = 1[/tex]