221 (1) 8x³+27=(2x)³ +3³+6) +0=0
(5a) = (2x+3){(2x)²-(2x)-3+3
= (2x+3)(4x² - 6x+9)
(2) a³-125b³-a³-(5b)³-84-81+3
= (a-5b)(a²+a (5b)+(56)²)
=(a-5b)(a²+5ab+25b²)
(3) 81x³ +24y³=3(27x³+8y³)=3[(3x)³ +(2y)³)
= 3(3x+2y){(3x)²-(3x)-(2y)+(2y)2}+dol
=3(3x+2y) (9x²-6xy+4y²)
(4) 4x-32x¹ = 4x(1-8x³) = 4x{1³-(2x)³ A
= 4x(1-2x){1²+1-(2x)+(2x)
= 4x(1-2x)(1+2x+4x²)