a/ \(a^6+8b^3\)
\(=\left(a^2\right)^3+2^3b^3\)
\(=\left(a^2\right)^3+\left(2b\right)^3\)
\(=\left(a^2+2b\right)\left(a^4-a^22b+4b^2\right)\)
b/ \(z^9-27t^{12}\)
\(=\left(z^3\right)^3-3^3\left(t^4\right)^3\)
\(=\left(z^3\right)^3-\left(3t^4\right)^3\)
\(=\left(z^3-3t^4\right)\left(z^6+z^33t^4+9t^8\right)\)