x(x-14)-(7+x)(x-4) при x=17/4

Раскроем скобки:

1. x(x-14) = x^2 - 14x
2. (7+x)(x-4) = 7x - 28 + x^2 - 4x = x^2 + 3x - 28
3. x^2 - 14x - (x^2 + 3x - 28) = x^2 - 14x - x^2 - 3x + 28 = -17x + 28

Подставим x = 17/4:

-17 * (17/4) + 28 = -289/4 + 112/4 = -177/4