Determine the degree of each of the following polynomials:

$x^{3}-9 x+3 x^{5}$

Factorise the following:

$1-64 a^{3}-12 a+48 a^{2}$

Expand

$(3 x+5)^{2}$

Find the quotient and the remainder when $2 x^{2}-7 x-15$ is divided by

$2 x+3$

Factorise $: 121 x^{2}-289 y^{2}$