Factorise: 

$x^5+1728x^2$

Factorise: 

$8a^4+27a$

Factorise: 

$x^2-8x^5$

Factorise: 

$a^6-64b^6$

Factorise the following:-

Factorise: 

$15625a^6-64b^6$

Factorise: 

$3a^7-192b^6$

Evaluate:

$\frac{{\left(0.68\right)}^3-{\left(0.13\right)}^3}{{\left(0.68\right)}^2+\left(0.68\right)\left(0.13\right)+{\left(0.13\right)}^2}$