If $x+2$ is a factor of $x^{3}+ax^{2}-x+30$,find the value of $a$.

Factorise $12 x^{3} + 17 x^{2} + 3 x - 2$.

Find the value of the polynomial $x^{2}-7x+12$ at $x=1$.

Factorise $144 x^{2}-289 y^{2}$.

Classify the following as a constant,linear,quadratic,or cubic polynomial:
$4-5 y^{2}$

Which of the following expressions are polynomials in one variable and which are not? State the reason for your answer. If the given expression is a polynomial,state whether it is a polynomial in one variable or not: $\pi x^{2}-\sqrt{3} x+11$