a) 4.(2a-b)2-16(a-b)2

= [2(2a-b)]2 - [4(a-b)]2

= [2(2a-b)-4(a-b)].[2(2a-b)+4(a-b)]

= [4a-2b-4a+4b].[4a-2b+4a-4b]

= 2b.(8a-6b)

b) 8x3-27y3

= (2x)3 - (3y)3

= (2x - 3y).[(2x)2+2x.3y+(3y)2]

= (2x-3y)(4x2+6xy+9y2)

c) 1/64x6-125y3

= (1/4x2)3 - (5y)3

= (1/4x2 - 5y)[(1/4x2)2 + 1/4x2.5y + (5y)2]

= (1/4x2 - 5y)(1/16x4 + 5/4x2y +25y2)

d) (x+3)3-8

= (x+3-2)[(x+3)2+(x+3).2+22]

= (x+1)(x2+6x+9+2x+6+4)

= (x+1)(x2+8x+19)

e) x6+1

= (x2)3 + 13

= (x2 + 1)[(x2)2 - x2 + 1]

= (x2 + 1)(x4-x2+1)

g) x9 + 1

= (x3)3 + 13

= (x3 + 1 )[(x3)2 - x6 + 1]

= (x+1)(x2+x+1)(x6-x6+1)

= (x+1)(x2+x+1)

Mình gõ hơi lâu mới làm được nhiêu đó thôi