因为 x² - 4 = 0
所以 x² = 4
x(x + 1)² - x(x² + x) - x - 7
= x(x + 1)(x + 1) - x²(x + 1) - x - 7
= x(x + 1) - x - 7
= x² - 7
= 4 - 7
= -3