8y^3-27

8y(y^2-27)

x^2+36=
(x+6)(x+6)

Facatoring completely
are they right. corrected if wrong

The first one is the difference of cubes

a^3 - b^3 = (a-b)(a^2 + ab + b^2)

so
8y^3 - 27
= (2y-3)(4y^2 + 6y + 9)

the second doesn't factor over the real numbers.