(8 x ² + 4 x + 1)(- 8 x ² + 4 x - 1)
=(4 x + 8 x ² + 1)(4 x - 8 x ² - 1)
=(4 x)² - (8 x ² + 1)²
= 16 x ² - 【(8 x ²)² + 2 · 8 x ² + 1 】
= 16 x ² - (64 x ^ 4 + 16 x ² + 1)
= 16 x ² - 64 x ^ 4 - 16 x ² - 1
= - 64 x ^ 4 - 1
当 x = 1 / 2 时,原式 = - 64 × (1 / 2)^ 4 - 1
= - 64 × 1 / 16 - 1
= - 4 - 1
= - 5