a) (x² - 1)³ - ($x^{4}$ + x² + 1) (x² - 1)
= $x^{6}$ - $3x^{4}$ + 3x² - 1 - ($x^{6}$ - 1)
= $x^{6}$ - $3x^{4}$ + 3x² - 1 - $x^{6}$ + 1
= ($x^{6}$ - $x^{6}$) + (-1 + 1) - $3x^{4}$ + 3x²
= -$3x^{4}$ + 3x²
b) ($x^{4}$ - 3x² + 9) (x² + 3) - (3 + x²)³
= $x^{6}$ + 27 - (27 + 27x² + $9x^{4}$ + $x^{6}$)
= $x^{6}$ + 27 - 27 - 27x² - $9x^{4}$ - $x^{6}$
= ($x^{6}$ - $x^{6}$) + (27 - 27) - 27x² - $9x^{4}$
= -27x² - $9x^{4}$
c) (x - 3)³ - (x - 3) (x² + 3x + 9) + 6(x + 1)²
= x³ - 9x² + 27x - 27 - (x³ - 27) + 6(x² + 2x + 1)
= x³ - 9x² + 27x - 27 - x³ + 27 + 6x² + 12x + 6
= (x³ - x³) + (-9x² + 6x²) + (27x + 12x) + (27 + 6)
= -3x² + 39x + 33
Chúc bn học tốt!!!
vote 5*, ctlhn nha bn
