If $x+3$ is a factor of $x^{3}+12 x^{2}+a x+60$ then $a=\ldots \ldots \ldots$

Classify the following as linear, quadratic or cubic polynomial

$4 y+11$

Write whether the following statements are True or False. Justify your answer.

$\frac{6 \sqrt{x}+x^{\frac{3}{2}}}{\sqrt{x}}$ is a polynomial, $x \neq 0$

Determine the degree of each of the following polynomials:

$-10$

Factorise

$x^{3}+8 x^{2}+9 x-18$