The first is the sum of two cubes, you have a formula for that.
The second:
(3x -4)(x +1)
1) 27x^3+8
2) 3x^2-x-4
2 answers
a^3 + b^3 = (a+b)(a^2-ab+b^2)
here
a = 3x
b = 2
You take it from there
(3x-4)(x+1)
here
a = 3x
b = 2
You take it from there
(3x-4)(x+1)