a) (3x + 2)³ - (2x - 5)³
= (3x)³ + 3.(3x)².2 + 3.3x.2² + 2³ - (2x)³ + 3.(2x)².5 - 3.2x.5² + 5³
= 27x³ + 54x² + 36x + 8 - 8x³ + 60x² - 150x + 125
= 19x³ + 114x² - 114x + 133
b) (2x + 7)³ + (5x - 6)³
= (2x)³ + 3.(2x)².7 + 3.2x.7² + 7³ + (5x)³ - 3.(5x)².6 + 3.5x.6² - 6³
= 8x³ + 84x² + 294x + 343 + 125x³ - 450x² + 540x - 216
= 133x³ - 366x² + 834x + 127
c) (3x - 9)² + (x - 7)³ - (3x - 1)²
= (3x - 9 - 3x + 1)(3x - 9 + 3x - 1) + x³ - 3.x².7 + 3.x.7² - 7³
= -8(6x - 10) + x³ - 21x² + 147x - 343
= -48x + 80 + x³ - 21x² + 146x - 343
= x³ - 21x² + 98x - 263
d) (2x - 9)(2x + 9) - (4x + 1)² + (5x - 4)³
= (2x)² - 9² - (4x)² - 2.4x.1 - 1² + (5x)³ - 3.(5x)².4 + 3.5x.4² - 4³
= 4x² - 81 - 16x² - 8x - 1 + 125x³ - 300x² + 240x - 64
= 125x³ - 312x² + 232x - 146
