1) (5x+4)(25x² - 20x+16) - 64= 125x³ - 100x²+ 80x + 100x² -80x + 64 -64=
= 125x³
Если x = 2, то 125 * (2)³ = 1000
2(2x+1)² - (x-5)(x+5) = 4x² + 4x + 1 - x² + 25 = 3x²+ 4x + 26
3) (x-4)(x+4) - 6x = (x-2)²
x² - 16 - 6x = x² - 4x + 4
x² - 6x + 4x = 4 + 16
- 2x = 20
x = - 10