You have to memorize the factoring of the forms (x^3 +y^3) and (x^3 -y^3).

x^3 +y^3 = (x+y)(x^2 -xy +y^2) -----(i)

x^3 -y^3 = (x-y)(x^2 +xy +y^2) ------(ii)

(1) (a^3)(b^3) -8(x^6)(y^9)

= (ab)^3 -[2(x^2)(y^3)]^3

= [(ab) -2(x^2)(y^3)]*{(ab)^2 +(ab)[2(x^2)(y^3)] +[2(x^2)(y^3)]^2}

= [ab -2(x^2)(y^3)]*[(a^2)(b^2) +2ab(x^2)(y^3) +4(x^4)(y^6)] ----answer.

(2) x^3 +27

= x^3 +3^3

= (x+3)(x^2 -x*3x +3^2)

= (x+3)(x^2 -3x +9) -------------answer.